Except the borrower would need to put down approximately $500,000 minimum, and he doesn't have that.He does have a few other SFR properties, but can't sell them in time to make the deal work.I told him he needs a private investor, but it doesn't seem he's going to find this. 

I am not sure if your loan officer would get a better payday but a safe bet is that if they do not have investments themselves I would steer clear of their advice until talking to others with investment experience.  

Because then your broker won't get paid on the your mortgage that he just sold to the actual lender, and that would make him sad.I'll bet if you ask someone who will make money by selling - like a real estate broker - they will say you can sell it as soon as last week.

I don't see why he wouldn't try to raise that remaining $120k privately, or go back to the bank. 

First you'll need 20% of the ARV to put down and then you'll need to reach out to private money lenders for the rest.

what is lot rent, what is the utilities....private or city water/sewer. 

How does someone in my position with the experience of finding the best deals, knowing multiple contractors for repairs, and the capacity to put it all together, find private lenders to fund deals?

Working with a private bank to see about 10% down with interest only until the property is built.

When investing with private money.

Rather than spend time looking for note investors, I'd recommend you look for private lenders or a bank that can provide you with funds at closing.