They also mentioned something about bonus depreciation as well.....

I'd like to tie this 'bonus' to the sale of the house, but I don't think that will help him, based on what he has told me.

I assume you can't structure your trading income as a salary with a bonus relative to profit with the person providing the capital (and maybe a forfeiture of salary if you don't make anything..)?

I have a friend who was applying for a mortgage and the bank requested documentation to prove where the large deposit made in August 2013 was from (bonus at work).

If your area is too expensive for you to move up comfortably, Oregon and Washington are great places to live, and WA even has no state income tax, a nice bonus.

As a bonus.

Could that make it a "bonus space" rather than a 4th unit if I sell it in the future?

I think the reason for this is that they are also trying to rent out a bonus room lacking a closet and therefore not considered a "room."

You could either take the money and use it towards a private or hard money loan to pay the down payment and do a couple fix and flip, or use it towards a conventional mortgage on an already flowing cash flow Property and enjoy the bonus income.

At some level are you just trading one income vehicle for another with the added bonus that you get the asset back (albeit there is a risk if the property gets trashed due to bad management) if the lender flakes out (and of course the hassle of calling the note).Hopefully some of the experienced private money lenders will jump in on this one, as it is a fantastic question.