Can he shorten his prayers and eat before leaving his house on a journey?

Firstly: 

There is no definition in the Sunnah of the distance that constitutes “travelling” and the scholars differed greatly concerning the definition thereof. The correct view is that reference should be made to the customs of each land; whatever the people customarily regard as being “travelling” is travelling in which one may break the fast and shorten the prayer. This is the view favoured by a number of scholars, including Ibn Qudamah, al-Maqdisi and Shaykh al-Islam Ibn Taymiyah. See the answers to questions no. 10993 and 38079. 

Secondly: 

The traveller cannot avail himself of the concessions for travelling until he has left his town and passed the boundary, then he may avail himself of those concessions so long as he continues to travel, until he returns to his home. 

It is not permissible for him to shorten his prayers unless he has passed the last buildings of his town or his village. It is not permissible for him to shorten his prayers when he is still in his house or town. 

The scholars differed with regard to his breaking the fast. Some of them said that it is permissible for him to break his fast once he has resolved to travel for sure and has prepared his means of transportation, but the majority said that he is not allowed to break his fast until it becomes permissible for him to shorten his prayers, which is when he has passed the last buildings. This view is stronger and is more on the safe side. 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:  

Is it conditional that he leave his village when he has decided to travel and has prepared his means of transportation, before he is allowed to break his fast? 

The answer is that there are two views narrated from the salaf.  

Some of the scholars are of the view that it is permissible to break the fast when he has made his preparations for travel and has nothing left to do but get into his means of transportation. They narrated that this is what Anas (may Allah be pleased with him) used to do. But if you study the verse – “but if any of you is ill or on a journey, the same number (should be made up) from other days” [al-Baqarah 2:184] – you will see that this view is not correct, because up to this point he is not travelling; at this point he is still a resident. 

Based on that, it is not permissible for him to break the fast until he has left the houses of the town behind. 

But before leaving, he cannot do that, because he is not yet travelling in a real sense. 

The correct view is that he should not break his fast until he has left the village. Hence it is not permissible to shorten the prayers until he has left the town, and likewise it is not permissible to break the fast until he has left the town."(Al-Sharh al-Mumti’, 6/346)

Based on this, it is not permissible for one who has decided to travel to shorten the prayers in his house, because shortening the prayers is one of the rulings of travel and one of the concessions granted to the traveller, and when he is still in his house he is not travelling. This is the view of the majority of scholars. There are also some odd views on this matter, such as the view of those who say that it is permissible to shorten the prayers when he is still in his house, and the view of those who say that he should not shorten his prayers if he travels during the day until night comes, and a third view which is that it is permissible for him to shorten his prayers when he has passed beyond the walls of his house. 

Al-Nawawi (may Allah have mercy on him) said: 

Our view is that when he has passed beyond the buildings of the town, he may shorten his prayers, but he should not shorten them before passing them, even if he has left his house. This is the view of Maalik, Abu Haneefah, Ahmad and the majority of scholars. Ibn al-Mundhir narrated from al-Haarith ibn Rabee’ah that he wanted to travel and he led them in praying two rak'ahs in his house. Among them was al-Aswad ibn Yazeed and another of the companions of Ibn Mas’ood. He said: And we narrated something similar from ‘Ata’ and Sulaymaan ibn Moosa. He said: and Mujaahid said: The traveller should not shorten his prayers during the day until night comes. Ibn al-Mundhir said: We do not know of anyone who agreed with him. Al-Qaadi Abu’l-Tayyib and others narrated that Mujaahid said: If he sets out during the day he should not shorten his prayers until night comes, and if he sets out at night he should not shorten his prayers until day comes. And it was narrated that ‘Ata’ said: When he has passed beyond the walls of his house, he may shorten his prayers. These two views are incorrect. The view of Mujaahid is contrary to the saheeh ahaadeeth which state that the Prophet (peace and blessings of Allah be upon him) shortened his prayers in Dhu’l-Hulayfah when he left Madeenah. And the view of ‘Ata’ and those who agree with him is contrary to the idea of travelling."(Al-Majmoo’, 4/228)

It is permissible for the traveller to join two prayers before travelling, if it is going to be difficult for him to perform the second prayer whilst he is on the road. But he cannot shorten the prayers before setting out. 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 

There is no set time limit for shortening the prayers or for staying in a place, according to the sound view, so long as you still intend to return to your homeland. But if you are intending to stay there indefinitely, then the ruling on travelling no longer applies in your case. 

The rulings on travelling begin when the traveller leaves his home and passes beyond the developed areas of his village or city. It is not permissible for you to join two prayers until you have left the town, unless you fear that it will not be easy to offer the second prayer whilst travelling."(Majmoo’ Fataawa Ibn ‘Uthaymeen, 15/346)

Shaykh Salih al-Fawzan (may Allah preserve him) said: 

If the time for Zuhr begins and you have not yet started your journey, then it is obligatory for you to pray Zuhr in full without shortening it. 

With regard to ‘Asr, if your journey will end at the time of ‘Asr, then you should pray ‘Asr in full at the proper time when you arrive. But if the journey will last from Zuhr until after the sun has set, and the time for ‘Asr will end whilst you are still travelling, and you will not be able to stop because you say that the driver of the car does not agree to stop, then there is no reason why you should not join the prayers in this case, because this is in excuse which makes it permissible to join the prayers. But they must be offered in full. 

If you pray ‘Asr with Zuhr, joining them at the time of the earlier prayer when you are still in your house and you intend to travel after that, then you should pray Zuhr and ‘Asr in full, with four rak'ahs each, and there is nothing wrong with joining them because it is permissible to join them in this case. But the time for shortening them has not yet begun, because shortening them is only permissible after leaving the developed areas of your place of residence."(Al-Muntaha min Fatawa al-Shaykh al-Fawzan, 3/62)

And he said: 

The rulings of travelling begin to apply when one leaves the town. If a person leaves his town of residence, by passing beyond the developed area, i.e., passing beyond the buildings, then the rulings on travelling begin to apply in his case, such as shortening the prayer and breaking the fast in Ramadaan, etc. But if he is still in the built-up area, then the rulings on travel have not yet begun to apply in his case. So he has to pray when he is still inside the built-up area, and he should offer the prayers in full at the proper times, just like the residents, because he has not yet started his journey. Even if he moves from one neighbourhood to another on his way to his journey, he is not yet regarded as a traveller, until he has passed beyond all the buildings and developed areas of the town."(Al-Muntaqa min Fatawa al-Shaykh al-Fawzan, 3/62, 63)

And Allah knows best.