It is absolutely legal from your point of view.  That is, any person may offer any other person a sum of money to do something which is not a crime, and there is no crime in withdrawing from an offer to buy something. So you would face no liability for doing this, at least so long as you don't otherwise do anything wrongful (e.g. there's no fraud involved). Whether or not the person with the offer can take your offer and withdraw without penalty depends on his situation--it's not impossible that he may owe some money to a lender or broker for that person's time; to the home seller if there are any limitations on why the buyer can pull out; or face some penalty if the HAP program includes one for doing this. However, that is largely that person's concern, not yours--you are free to make the offer.