Concentrate on savings, living frugally will be your best approach to increasing savings.

I was hoping to refi in a few years and get cash back out at the new value after rents are increased.

Comparable sales on 3 Bedroom two Baths in the area is from $120,000 to $150,000 move in ready as this one is the $15K delinquency is PTI and increasing every month, and the owner finance buyer bad credit will not allow refinance as you suggested Jay.   

I also made mine taller, which should increase the stack effect and make them more efficient.

She agreed, I gave in to resistance and increased my cash flow.

Here are the numbers I've calculated  based on 80% refi of all 3 properties, at 30 years, at 5.25%:Item                              Current                 Post-RefiCash available         $        0                   $300,000 +/- Cash Flow/Year       $   65,000              $  52,000 +/- Re-invest $300k from Cash out as 20% DP on more properties (there's an even better way than this too)& using the same ratios of ARV to NCF, you could increase your NCF an added:  $78,000/year; to $ 130,000/yearYou are sitting on a Gold Mine here, and you're thinking like a "homeowner"...not an investor...although you're not alone.Your Options:  Limited by the maximum Cash Flow from existing properties after complete payoff Max CF/Year                                                                                    =  $   95kCost to do this (pay off all mortgages using your cash)          =  $  456kNet result                                                                                        = - $ 361K  (that's a loss)REFI ALL Option:  Limited by ???????                                                                                                             

I would talk to your CPA first.I have bought at year end to decrease my liability and or increase my passive loss from year to year..

Also, any good books I should be reading to increase my knowledge of real estate?

Most MFRs I've seen are at 0.6% - 0.8%.Look at MFR sales in South BostonIn 2013, there were 39 units sold, with an average price of $727,949 and 37 days on market.In 2016, there were 36 units sold, with an average price of 1,272,467 and 50 days on market.A 73% increase in 3 years.3 bed rentals in South Boston over the last 3 months averaged $3,346.I've felt for a long time that the better deals are found south of Boston in Plymouth and Bristol counties.  

Whatever income the new buildout would produce would increase your value.