I think you may want to go back and do some more research and reading, get a few books, listen to some additional pod casts and refine some of the methods used to find deals.There are a ton of ways to find property:Direct maildoor knockingnetworkingcraigslistcall adds or signs for rent and ask current landlords if they are willing to selldriving for dollarsMLSvarious RE agentsdelinquent tax records/paper publicationsre-purpose a buildingetc etcIf you were looking for MFH then yes switch to SFR.

Ease of exit, possibility of appreciation, generally longer tenancies and superior tenants, etc.Really, you should evaluate every prospective deal on its own merits, and not worry about whether it is "good enough" relative to other hypothetical deals that are not in front of you.  

I don't think that method qualifies for Fannie/Freddie loans, so I'd have to find a portfolio lender who is not looking to sell the loan.

This is the method Sean Terry preaches as a good way to build a team.

's method and taking out a HELOC on this house?

If you acquire a 3-4 unit property and there are tenants there already, what is the best legal method you have done to remove them so you can pick your own tenants base on your screening methods. 

  :)  SOME (not all) may frown on this method.

I used the strong letter method because 2 days before closing a new loan on my building, (that was in foreclosure and receivership..not my doing, partner problems) the bank changed their mind on making the loan!  

Lots of good info in this threadhttp://www.biggerpockets.com/forums/311/topics/125040-how-do-you-scale-your-business-so-quickI have went from 4 units to 42 units in about 3.5 years using the land-contract purchase/small bank refi method.

You're clearly at an early stage to this process where it may be best to talk with an architect, they'll be able to consult with you about feasibility, code restrictions, permits, space planning, construction methods etc.