I'm trying to buy a 4 plex, and live in one of the units.The problem is that the rents are currently too low for the apartments to cash flow with all four units, and the rents would just barely cover the mortgage if I lived in one of the units.I could live there practically for free but what would I do when I wanted to move?

The larger benefits you get from investing in residential real estate are from the mortgage pay,down and the capital appreciation over a long period (as prices can always go down in the short term). 

Sure if there is enough margin to cover both mortgages.

The IRS also will typically negotiate for pennies on the dollar if you don't want to wait the 10 years.IRS liens and state treasury liens are the only liens (including mortgages) that I know of that are not extinguished when a tax deed is issued.I have cancelled getting a tax deed in the past after finding out there was an IRS lien against the property.

Call Kerry Gelbard at LA Mortgage. 

If mortgaged then no liability anyway.

The investment banker mentioned that the tenant can/will take over paying the mortgage, but I don't really know the details yet and what is best - for me and the prospective renter/buyer.If we don't do this rent-to-own deal, I can get a tenant in within one month. 

I have put 20% down on the three rentals and financed them with 30 year fixed mortgages (3.75-4.5APR). 

Im talking about rehab fix and flip stuff, not long term mortgages.

If I do would I still have the mortgage payment charged to my personal checking account since it would be my permanent residence as well as an investment?