A 4-plex (strictly for investment) really caught my attention and according to rentometer, I can increase the rents by $275,  per per unit.

Alternately you could send them all a notice explaining the situation and indicating that if there is another fine that you are simply increasing all rents to cover the potential costs. 

but your taxes and HOA will increase as well. in a downturn you go negative. 

Send in a ton of paper work FEIN, rent rolls for SFS, 3 years of tax returns, 24 lease agreements, contract, p&l on complex, I gave them a 5 year plan of expected rent increase vs expenses.Scheduled walk thru- Due diligence time.

Now we need to give her rent increase notice, can we increase her rent based on $650?

I looked at New London and think it's a fantastic town, probably going to see increases in value IMHO: its got great "bones" as a city, is starting to "urbanify" (trendy places starting to open) but it's way behind the curve, and it seems to me the hipsters there are still young and haven't started having kids/figuring out how to make the city work with kids--so prices are dirt cheap.

But the best and most invaluable part above and beyond your increased ROI is the hands on experience.

I not only help prevent a foreclosure which ruins your credit, I increase their credit by paying off their mortgage of a house they (more often than not) no longer want.

My attorney advised that I could put up a non-refundable option fee for maybe $100 - $500 dollars for a period of time that goes by and then increase for each # of days that goes by in the contract, so for instance:(Option Fee - not Earnest Money)$500 give to seller 3 days after contract is signed.If close hasn't happened within 15 days, give them another $500.If close hasn't happened within another 15 days, give them another $500. 

Tenants tend to think “automatic massive rent increase” when they hear a property is for sale.