I have been looking at S8 housing for about a year and have not pulled the trigger. But plan to in 2016. My assessment is that it takes a good business model to support it. Forgetting for the moment the low cost financing and tax credits.
I can only speak to Jacksonville S8.
The rent is guaranteed, that is huge. No collection, no late payments. Evictions are easier and less costly S8 will help you. There is a 2 year waiting list in Jacksonville to get a house, these people do not want to lose their place. There are good and bad people every where and you will run into some of each. Your maintenance costs will be higher, however you can use lower quality materials and labor. The numbers must also support property management. It is worth the expense to have someone who specializes in that market.
Appreciation is unimportant to me. These are all about cash flow. I would take cash in hand over the promise of equity in a building. You would need to borrow money from a bank or liquidate the building to get at the money.
I think equity is a fallacy, if you own the building outright then that is one thing. In the event of crisis like 2007, you would be better off with less equity. If you have greater cash flow, in a down turn you would be more likely to be able to cover the debt service. In the event you can not cover the debt, it will be unlike you will be able to sell the property. The cap rate will not be sufficient to another investor to buy. In this example the cash flow, would still be high enough to cover the debt and ride out the crisis. Furthermore, the bank would foreclose on the property with equity first.