Looking for advice on a nightmare tenant

[Manuel Luz]

Hello, so I bought this property 2 years ago, 4 unit in fairhaven mass

All tenants are severely undermarket, 1 i came to an agreement with to increase rent(nice quiet guy wanted to keep him) 1 is special needs(he's the last one ill deal with) the other two are...drama and needed to go.

So 2 months before their leases ended i told them i was going to be going up in the rent(in hopes they'd clue in and find somewhere to move) In turn they started withholding rent to which i initiated a notice to quit and in response they went to the board of health which resulted in a large itemized list of repairs that needed to be made. Trivial stuff(cracks in walls, baseboard, kitchen cabinets not closing properly) that basically required a remodel of the units. At the time i was relaying on peer advice that they cant withhold rent for such things and i felt i had a strong case for eviction. 1 of the women agreed to move out through mediation, the other we ended up in front of a judge and she won possession of the property. 

So I remodeled the vacant unit had it inspected and certified by the BoH and came to an agreement with the tenant if she moves downstairs she will begin to pay rent again. This allowed me access to upstairs and continue my remodel. I completed this remodel got it certified and rented the unit out in april. 

And i write this to you now because the man i have rented this unit out to is now dating the women downstairs. This is giving me some anxiety because i've seen how this woman operates(placing mice droppings to report rodents to report to BOH and calling the cops on me when I tried to make repairs to her unit saying i showed up without notice) and I fear this may turn into some leverage move by her when I either go up in her rent or ask her to leave. Her tenancy is at will now but with this pandemic and courts being closed and i assume backed up when they do reopen I'm not sure what my next steps should be. 

I know she will not leave without a fight. So either way this is going to require a court order. She has a slue of medical conditions(which i strongly suspect are just hypochondria) and 2 teenage children. These will all be used along with any other reasons for her inability to move out. 

She is about $300 under market. I know that mass has no restrictions on rent increase as long as there is 30 days notice but I'm not sure if raising her rent to market in one go or if raising her rent incrementally over time(like in a 6 month span) will look fair infront of a judge. 

I feel her winning possession of the property and keeping the 3 months of withheld rent(and additional months after while remodeling the other unit) was very unfair so I'm paranoid now and want to consider every angle i can. Either way im going to be in a long draw out case.

I know I should and will be consulting a lawyer but in the mean time i wanted to vent and see if anyone experienced with tenants in mass have any insight for me. Sorry for the novel lol thanks for reading.