DCRA is a disaster. We used RentJiffy. Best money we ever spent. I think it was $400 all in (so a $210 premium over the DCRA fees.) They have an online application, walk it through DCRA and get you a permit. They also walk you through (for free) what you need to concentrate on for the inspection. (I'm not a Rent Jiffy agent, but the experience was so great I'm happy to shill for them).
The DCRA inspector may flag all kinds of stuff. Water heater expansion valve in your house? It's required now. Hand rail on deck stairs? DCRA also has strict rules on locks (no double deadbolts on exterior doors). New locks can run you $30-$50 per lock. Have bars on your windows? If they are the only egress then they need to be able to open. Unless you are handy with a blowtorch now you're hiring someone to redo your window bars. Your fire alarms need to be within 10 feet of each bedroom (bit not inside). If you needed to have those rewired you are going to be out more money. We spent between $3-5k getting the house ready and then making DCRA happy.
Deep clean from housekeepers was more than $200.
Our tenants have a young kid. Little known reg in DC that requires you to have a lead test before you rent to young kids or pregnant women. That was another $400-$600 (per swab fee, and required to do a swab in each room on window and floor).
Our insurance went up but only by about $150 a year.
Background checks on tenants are @$75 per person. If you are eating that then it's an additional cost to consider.
We found our own tenants so we didn't pay an agent's fee. And we are self managing so we saved another month's rent fee (8%). But you could easily lose two months (one for finding tenant and one for managing).
We already had a service contract on mechanical stuff that included labor. That was @$400 year. I will probably keep it next year since it means if there are heat/AC issues the tenant can call for service and I don't have to be bothered.
Loss of homestead deduction isn't where you will feel pain (that's only about $600/year.) What will get you is the fact that the property tax cap won't apply. You will pay full freight. This year, next year, every year. Depending on how long you have owned your house and how dramatically assessments in your area have increase, you could be paying on more than 6 figures less than actual assessed value. And that # will catch up as soon as you eliminate homestead deduction.