I work for a HML and we give out lender letters all the time to increase the borrowers chances of closing.

I took the math a bit farther and did some calculations to see what it would look like to borrow from my 401k to put into more real estate deals.

I left buying rentals in the metro area in 2014 as the hedgefunds moved in and retail found they could borrow again.  

We talked about it and during the conversation he said he could borrow money from the bank and that would cost him.

They don't much like to do it with large construction loans, unless they get paid huge fees by the borrower.

Earlier is better, of course.You will need an authorization letter from the borrower, allowing the lender to talk to you.

HMLs have a totally different criteria to borrow. 

Have you all dealt with banks and borrowers before?

Must be the borrower's primary residence.Based on that, you would have to refinance out to a different loan if you planned on moving out. minimum FICO of 660 for single family homes. 700 for 2-4 unit homes.Must not exceed 100% of the annual median income for your county, which is $76,000 for Cook County Illinois as an example.You can use their eligibility tool to look at other areas. https://homeready-eligibility.fanniemae.com/homeready/

Also, if it is a note secured by real estate it will be best to list the IRA in firs position in the event of default by the borrower.