@Bassim Audi how exciting! I would echo what the others have said and add a few more things. I have a portfolio of Section 8 rentals in the St. Louis area. I've bought 14 tenant occupied properties over the last 18 months, about half had Section 8 tenants.
First, I'd ask for the current HAP contract or most recent Notice of Change for every unit. That's the documentation from the Housing Authority that lays out how much the tenant pays and how much the Housing Authority pays. It will also tell you when the annual recertification is for the unit/tenant, which may tell you when an increase can be requested (it would here, see below, but may be different there). Then I'd ask for a ledger for the last 12 months for each unit for the HA portion and the tenant portion.
Next, I'd try to find a local landlord who has been successful with Section 8 in the area that you're buying. There are more Section 8 horror stories out there than success stories in my experience but it can be done well, so don't listen to the naysayers. I'd ask that person what rents they're getting as well as some tips, tricks, info on working with your Housing Authority. Every HA operates differently so they each have little nuances that can be learned and utilized to your benefit.
Here we can only submit for a rent increase 60 to 90 days prior to the annual HAP contract renewal and if we miss that window, we have to wait until the next year. I never miss this window, btw!
I have found that my Section 8 tenants have been fine during COVID because if their income situation changes due to job changes or loss, they simply submit new income paperwork to their caseworker and the portion of the rent that they pay is adjusted accordingly. I am currently owed $0 in past due rent!
I do increase rents on my Section 8 properties to market rents even with existing tenants. It hasn't generally negatively affected how much the tenants pay in rent (the tenant portion). I also haven't had issues with existing Section 8 tenants leaving over rent increases.
Lastly, I've found that the tenants expect some changes with a new owner and depending on the last owner, may welcome it, including a signed lease because it makes it very clear who's responsible for what and leaves no gray area. If there's repairs that need to be made, we give them a list of the repairs we're going to make and on what timeline and then we do it. That has helped tenants to know that we will do what we say we'll do, including sticking to the terms of the lease. Again, my experience with this has been almost completely positive.
Let me know if I can help further and good luck!