Is it permissible to postpone fulfilling a vow to slaughter a sheep due to a lack of financial capability, and can it be slaughtered in a place other than in front of the house due to the impossibility of doing so, knowing that the vow was to slaughter it in front of the house?

If you hope to be able to fulfill your vow, then it is obligatory for you to do so whenever you are able. As for the place of slaughter, there is flexibility in the matter; you can slaughter anywhere, even if you vowed to slaughter in one place and distribute in another place outside the Haram (sacred precinct). In such a case, you are permitted to slaughter wherever you wish, and you are obligated to distribute to the poor of the other place.