Are there any reputable lenders today allowing 80/20 combined loans?

If you get a reputation for wasting everybody's time, nobody is going to want to work with you.

 @Elizabeth Colegrove  Is it smart to find a bank that does portfolio lending as well but first exhaust the conventional methods, build a reputation then work my way up to the lending managerOrFind any bank that will finance my first deal, try and repeat the process a few times and when I need a portfolio lender just start searching when I cross that bridge.

While I was interested, (not for a profit, however) my instincts told me to be careful and not rush into things as my reputation was at stake if his data or service was questionable. 

If they are well established and have a reputation, you are at less at risk of them losing your reserves.

If you use the weasel clause too many times you will get a reputation in your town as someone who can't close.

I don't believe that a properly worded letter of intent will be a legal issue; it is just a matter of reputation, and basically doing business transparently and honestly.  

I care about my reputation and my REI Students.The bust from the CFPB - not underwriting the Buyer on a seller financed deal - is 36 monthly payments, down payment, lawyers costs, courts.1% fee from the RMLO to look at a 1003 app and give an opinion is basically a cost to do business in the USA on Rent to Own.Many will not agree with me.But I would rather have me and my home seller protected.

Keep in mind, their reputation is on the line, too! 

So, on that front, can't say, but there is also your reputation, you can trash that before you get started too.Moral of WH, explain up front to an owner as to what you are doing, they are to be fully informed, use an option if you can, not a contract with mickey mouse exits as the con artists do it.