I'm an investor and agent in Western PA (Greater Pittsburgh market). I am biased but I think Pittsburgh is one of the best section 8 markets currently.I've been doing section 8 rentals since 2010 as a property manager. It has had its highs and lows in Western PA. For example, a few years back they were really be stingy with approving for top approval rents because landlords were trying to get top rents but their places were barely passing hability standards so they were approving section 8 but at lower rents. More recently they seem to be just trying to get as many section 8 renters into places as possible.
Section 8 here has a predetermined rent amount (max allowance) for each property depending on if it is a house, apartment, townhouse, etc and what utilities the landlord pays versus the tenant. Depending on the areas you choose you can have fantastic cash flow. What @Alyssa Wright stated is correct. If you have a clean, properly marketed unit you can get an approved section 8 tenant within 7-10 days. It does take about 30 days for section 8 to send out an inspector and approve the unit for move-in but all in all it can be a pretty quick process. They have actually shut down new section 8 applicants for people who want to get on section 8 because there are so many existing renters who are looking for housing and so few landlords that want to do it. Because of this, it isn't uncommon for a section 8 tenant to move into a unit and stay 3, 5, 7 years or longer.
Hope that helps!