If we increased rents to match those (after renovation, of course) the cash flow would be $750/month.

My instinct suggests: sell both of them, and put it all towards that forever home that may very well become increasingly out of reach if you don't.

(Rule of thumb suggests that falling below 1% gross return per month makes it increasingly hard to cash flow positively on average, when borrowing to the max).A similar question: Are you getting a bargain* (compared to sold comps)?

The upper unit is fine, and no walls need to be opened.The electrician says it would costs around $8k to  put separate meters , panels and rewire upper and lower unit as needed.By separating the electric, by how much would it really increase the value of the two family?

Personally I would flip houses Each time increasing the investment cash I have until I could buy an apt complex to replace my income

Ideally the property would have one meter that all the units share, and one solar system that feeds that meter.Lastly, leasing is increasingly less attractive to new solar customers. 

If a MFR produces 10k of operating income and is valued at a 10% CAP rate, the value is $100k.Assuming the CAP rate holds relatively constant, the value won't increase until the cash flow increases. 

However, NY state law limits the increase in assessed value is capped at 6% in a year or 20% in five years. 

Stephanie That's right Stephanie, the borrowers can qualify all day long but if the property doesnt meet the SS rule then they are going to have to use a 5/1 ARM, bring more down payment down, buy down their rate, or increase the rents prior to the appraisal (great strategy but hard to implement) in order to get those rents to be equal or > the monthly PITI.

Scenario A (typical) - $500k duplex-$125k down-$375k mortgage at 4.6%Scenario B (modular financing) - $500k duplex-$125k down-$260k mortgage at 4.6%-$75k HELOC on primary residence-$40k loan against 401(k) (technically this would be $165k down, but you get the point)In scenario A, paying off the mortgage quickly makes zero improvement on cashflow until you pay it off completely, or refinance, and there's no point in that if your rate is locked in lower than current(or future) market rates.Scenario B could involve higher interest rates on the HELOC and the 401k loan, but you have multiple, simple, easy options for increasing your cashflow, and then you don't end up playing as much in the overpriced, volatile stock market.