@Roberto Hernandez, you mentioned that you had a 9 year goal to retire. That means you're going to be better served by investing in cash flowing properties than properties that appreciate. The reason being that cash flow is more predictable and stable than speculating on appreciation. Yes, there is an argument to be made for appreciation and refinancing when you need capital, but then you're going to be at the mercy of market conditions (interest rates, how the economy is doing, etc).
With that being said, the next step is more personal finance than real estate. You're going to need to know how much cash flow you need (expenses, saving for rainy day fund, saving for primary residence, saving for kid's college, taxes, etc). This annual cash flow requirement is the target cash flow income you would want your rental portfolio to have.
After that, I would just look at what places are renting in the areas you want to invest in and the cost to acquire/operate the properties (mortgage, insurance, maintenance estimate, etc) .
Personally, all my properties are not in the DMV area. This is because it's been easier to find cash flow deals out of state. The price to rent ratio isn't as good as other states like Ohio or North Carolina.