Initially, I thought that I could get the property FHA conforming  by adding a fridge and a shower.

This will be right before the washer breaks down because it's doing load after load of diapers every day, the microwave breaks down because it's busily heating up formula and breast milk every day, the range starts a fire because the boyfriend is careless about leaving the burners on, the fridge breaks down because he's doesn't give a damn about about making sure it's shut.It all amounts to a compassion tax they're demanding that you pay because they had the shrewdness to break their lease and you had the stupidity to be a landlord.So get rid of them.

I want the fridge to be white, too.

There's been a water leak from the unit above us for almost a year and so drywall and paint chips have all fallen behind the fridge and I'm just not cleaning that up, so I'll be back to update within the month.

If you unplug your fridge and plug in a new fridge, that does not typically require a permit.  

I would just make sure you write something up along the lines of "The leases states I am not liable and tenant should have renters insurance, but this one time I am offering X and if it happens again the tenant will have to use their renters insurance" If a tenant's fridge breaks, I compensate them for spoiled food. 

My concerns: No previous rental data on MLS for that unit, current tenant is occupying only upstairs part of the unit (with no kitchen, has his own fridge), As per seller's agent paying $500 and said he may leave at request.

It's not a problem that you bought a triplex -- the problem is that you bought a presumably old house with electrical issues.Thats true, but having 3 fridges running in 1 house along with space heaters... and 2/3 being on the same breaker.Also the Breaker box being in the basement of unit 1 and the others needing access. 

Used older house doesn't need a new a/c or a new stove, fridge etc.

But, they can change the fridge filter.