This topic was in a legal advice forum a few days ago.
But from the other perspective. The new owner was already in the house but the payment was not complete.
The new owner then wrongfully withheld money due to defects. Whether those were defects was also disputed.
I myself also sold an apartment back then. I deliberately postponed the handover to avoid problems and to avoid having to live somewhere in between. Of course, we needed partial bridge financing for that.
You also have to consider that the transfer of ownership also entails obligations for you if the current owner still lives there.
That can mean anything from simple repairs to loss of rent or even eviction lawsuits, etc.
Do yourself a favor and do not deviate from the usual contracts. Set deadlines for when what must be paid and what happens if construction by the old owner stalls, because you have costs, such as interest, the ongoing rent that must be paid, and so a double burden quickly arises. If he does not move out, charge rent and set it quite high.