Check out Fannie Mae Desktop Underwriter guidelines for what they're looking for because that's all the lenders are doing -- selling to Fannie Mae and Freddie Mac. I had terrible times with my triplex and a duplex with a cottage detached in the back yard (with it's own lot); both considered unconventional. That's 80/20 LTV because who can pay PMI? Cross collateralization is the only way I know to buy anything with no money down. Also, living in the multi helps the lender feel better about the property. Of course, you lose owner unit writeoffs if you do that including that portion of depreciation.
The points ffrom my lender changed from 1 to 21/2 the day of closing by because the loan officer claimed it showed up "flagged". Lenders don't like multi like tris and quads because they know they're harder to get rid of and they are...because Catch 22 they're harder to finance.
Don't forget insurance.. Anything over 2 units, State Farm sees in a different category in your rental package. When buying older properties, make your first call to your insurance agent before you offer and close the deal. And never lie about number of claims to any of them. They don't hesitate to drop you in a minute.
Also, on a mult--check with city zoning and make sure it's grandfathered to have the units being sold to you with a certificate. Alot of neighborhoods downgrade zoning and don't address this certificate and after you own the property, the neighbors complain and they want you to reduce your property to a duplex or single family. This matter can cost you time, trouble, and money. Should be in the contract for the seller to "fess" up about the zoning. Nobody helps you on this. Be careful.