You could try to value it with the income approach, with NOI & DSCR, but that usually isn't done with smaller multifamily.You're going to have to extrapolate out farther and see where other smaller multifamilies have traded.

Again even if you have great credit as you start to add more credit cards, mortgages, auto loans to your credit you can also be viewed as "High risk" due to Excessive trade lines in credit or higher DTI - debt to income ratios. 

I traded up for a 7 unit apartment building.

I also have a $50k line of credit I can tap into when needed that will grow as I keep growing the business.Right now my rent is about $1700 where I've been staying for over a year, but really wanting to trade that for a mortgage and start building that equity.

To defer all of your gain, you'll want to trade up in value, replace all the debt (meaning new properties have at least $350,700 of debt), and not take any cash from the exchange (this is boot which = taxable gain).As for replacement property, it just has to be real property - meaning it can be commercial, STR, land, etc!

When I was 22 I had to move from my home town to Las Vegas in pursuit of HVAC trade school.

Sure, they may be able to grow to a very moderate size,  add a few units, or trade up to a larger investment, but as for real scalability: NO.Why?  

The operator may trade off the longer term benefits to keep a high quality tenant in place.

To answer your last question, my realtor has contractor contacts I should be able to leverage for rehab budget estimates, as well as family friends with experience in the construction trades.

We have trades we use on jobs and know what they will charge which is often considerably less than what Joe Homeowner would pay for the same job . . . the trades know we will be using them again and again.