Too many people staying in my house not on the lease
I'm looking for some solid advice. I rent a small 650 sqft single family home to a long term renter of like 10 years or so. It's a two bedroom one bath. The floors were recently replaced with new LVP last year, new sink and countertop this year, new hvac this year. I do my best to keep up with the property. The tenant pays $700 per month in rent and I haven't increased that in some time due to her being on a single income. I told her I was increasing it to $750 this year, and I need to put some kind of clause or something that stops all the other people from living there.
The tenant's boyfriend, and two sons have also moved in and are living with her. One is living in the unfinished basement which is not fit for anyone to live in there. I believe there is probably mold down there. The house has a underground stream that runs under it and it is very difficult to keep the basement dry. Measures have been taken but it seems like its never 100% good enough.
I was thinking about adding some kind of verbiage to the lease agreement along the lines of, "any persons staying in this property for more than 90 days will result in an additional $150 fee per month added to the rent" or something like that. My thoughts are that when I add this to the rent this will become the renter's problem and she will work to evict her family from the house (assuming they don't pay her the $150). She has always had members of her family staying with her and the extra bedroom is always occupied by someone not listed on the lease. I don't mind when people come and go. But long term stays are adding to the extra wear and tear on the house and I have no additional compensation to keep up with cap ex, repairs, etc.
This is a long term tenant that's basically family at this point. I have no intention of evicting her. She has mentioned to me in the past that she wished I would evict her son from the property. I've never had to deal with eviction, and I don't know if I can evict someone not found on the lease that she willingly let stay there. These people have overstayed their welcome and it isn't clear who is responsible for getting them out of the house. I would hate to think it's my responsibility. I feel like there may be multiple options I can take to try to resolve this. Could anyone more experienced give me some advice? Thanks in advance!