As for the rental, generally, we'll need to register with the city and they might come with inspection (happened twice to us) so make sure that the conversion is up to code and the list of the requirements are met. 

You could also try leaving 1 garage and making less massive master suite but check local code on shard wall with garage. 

You might want to consider Quincy also and Malden for more price friendly zip codes but still being close to Boston and transit. 

Liens that remain generally are unpaid taxes, and involuntary liens including but not limited to code enforcement, unregistered permits, unpaid utilities, etc 

Legally and morally, you should honor the contract, just like you would expect the renter to honor it.

Every circuit should have a separate breaker according to code and safety.As @Jaron Walling said, it's a simple math equation.

@Jaekwan LeeA house hacking inspection checks for structural integrity, roof condition, plumbing, electrical issues, HVAC systems, windows, insulation, base and attic damage, unit conditions, and code compliance.

Depending on the zip code you might also check with Wells Fargo to see if they offer the down payment assistance grants in that area.Could be the buyer is just trying to save cash, so counter back with no closing costs.   

I looked at almost every market in florida before I relocated from columbus ohio because miami Dade County has the most net migrations in the entire United States for one county. we build it in columbus ohio and it is worth approx 215k a door but down here all you'd have to do is change the assemblies and in miami that triplex would be worth more than 300k per door so closer to 900k depending on where you built it. new construction single family homes are going for around 330 per sq ft in the same area and a triplex is considered residential. by building codes a 4 unit is commercial I'd recommend 3 unit first or going as many units as possible if you have backing or your own cash. for each one we do we recommend 100k of liquidity. 

The kicker here is that they don't always honor their leases.