Are you assuming they are lying to you? Or are you assuming you should buy them all and list them on the MLS for $820k, clear $770k after closing costs and put $120k in your pocket?
How much of the $650k do you have to borrow them to complete the build? If it’s over $150k it’s too thin. You need margin for the point it’s 80 or 90% built and the builder says they’re out of money.
I hear you now. “No, I’ll release the money on draws, that won’t happen…” Ok, so you need margin for when it’s 50% done and they say they can’t afford to get to the next draw point. Give them money or they lien the house and walk off the job.
MAYBE I’d buy the land and lend half the building COST while the builder puts up the other 1/2. Then you agree to buy them out for 1/2 the difference between $650k and cost? Like a partner would? You being a “partner” and then paying the “profit” to the builder makes no sense. Anyway, as long as this is money you can afford to lose good luck. I love the idea of new fourplexes being built. But I haven’t seen one pencil in a long time. You could look at “FIG” (fourplex investment group) I get ads from them occasionally.