@Amanda Eyler Congrats on the potential deal. I'm a Section 8 landlord in the St. Louis area, with 26 units. I love the niche and think it's the most stable and profitable rental niche out there when done right.
I've bought several units with Section 8 tenants in them. It's on my list to write a blog about how to do this but for now, here's what I'd recommend.
Ask for the most recent lease and/or notice of change/annual recertification for each tenant. This is a document from the Housing Authority that lays out how much the tenant pays and how much the HA pays. Then request a rent ledger for each unit for both the Housing Authority and the tenant. It's best if those 2 ledgers are separate, otherwise, it's hard to decipher but not impossible.
I'm assuming you know to ask for the leases for each unit as well, but if not, do that as well.
As for the units not being well cared for, this isn't uncommon unfortunately. There are great S8 tenants out there but landlords/property managers often aren't great about tenant screening (market or Section 8 tenants). What I do in this situation is I buy the property with enough margin to allow for both immediately needed repairs and a good rehab once the tenants leave.
Then immediately after the purchase, I meet with the tenants and give them a list of the planned immediate repairs. I tell them that we're going to being making these upgrades and will be an attentive landlord. In return, we need them to begin taking better care of the property, and we give them a list of things we need them to do, now and moving forward.
During the lease, make sure you're enforcing the provisions of the lease and upholding your responsibilities. If I have tenants not following the lease, I notify them the first time and don't do anything further. If I have continued problems or it's a serious issue, I notify both the tenant and their S8 caseworker.
Rent increases through Section 8 are usually pretty easy to obtain but many, many landlords miss this. I recommend finding out your Housing Authority's process for increases and following it to get them.
Lastly, when the tenants move out, you should receive a "Good Standing Certification," in which you can certify if the tenant is in good standing or not (monies owed, lease violations, etc). If they aren't in good standing, they aren't supposed to be able to get a new voucher to move until they are in good standing. I think of this as my safety net in case there are major issues unresolved (tenant damage that I've repaired and not been paid back for is one I've dealt with on inherited tenants) that help to make me "whole" before move out.
Again S8 is a great niche but many people don't learn the processes and rules and try to run them like market rentals. Landlords who learn and master the processes are most successful. Those that don't often end up hating the program.