My question is : what would be sufficient return to interest commercial investors for my area?

I assume you mean to say that you registered yourself with your state comptroller (or Sec of State) for Doing Business As (DBA) some fictitious name.For your DBA activity, use Schedule C (1040) on your personal tax return to report your business income and expenses. 

After a completed first purchase and property management have proven themselves, then I consider it a lot less important to return to the area for a first hand look at additional properties.

If this is an old 401k - you can easily roll it over to self-directed IRA. 

You could easily go check them out.

When you find a pretty solid SFR Buy n Hold investment property is reasonable to just look at the Cash on Cash return or should the market purchase price be a significant factor?

You are overpaying for a building that could easily have more problems than you know.  

Just stay consistent and you should have a good return on investment. 

The point as I see it is that an additional ELOC or refi of the FIRST one will put a strain on ITS cash flow, but so long as it isn't a negative flow, the amount cashed out should easily be able to act as the full deposit for the second, so the rest could be fairly conventional.And of course, the second one needs to have a SIMILAR order of built-in equity, and so on!...

Also all of the appraisers seem very conservative when they look at something you have bought recently.You may get lucky and they give you the value you are looking for, I'm just saying don't count on it and don't be surprised when they return an appraisal of $110k...