Can this be done nights and weekends or am I kidding myself

Ten hours a week is enough to build the buyer side and not enough to compete on the seller side. That's the honest shape of it.

The buyer work is calls and coffee. You can do that at lunch and on Saturday mornings. Finding a house at 65 cents on the dollar in a market where twelve other people are mailing the same list is a volume game, and volume is hours. You don't have hours.

So the part-time version usually looks like one of these. You become the person who brings deals to a small group of buyers when you stumble onto one, maybe two or three a year, and you treat the fee as bonus money rather than income. Or you narrow to a source of properties nobody else is working. Around here that's been probate-adjacent leads and small landlords who are tired, both of which reward patience more than speed, which suits your ten hours better than a dialer would.

On your question about the buyer moving on. Yes, he will buy from whoever brings it first, and that's fine. You're not holding an order that expires. You're on a list of people he'll take a call from. That relationship survives you being slow. What kills it is bringing him three houses that don't fit his numbers, because then he stops answering.

The 12k mostly sits idle in this model. You need earnest money and an attorney hour, not capital.

If what you actually want is income without a second job, say that out loud before you spend a year on this. This one is a job. It's just a small one.