Unless you have the rentals paid for by the time you retire, they aren't going to be enough to live off of. 

@Tiarnan GormleyStarting your real estate journey while living abroad is ambitious but entirely achievable with careful planning.

Hey John,I own 12 units in Detroit but currently live in California.

Hello, I live in southeastern Wisconsin and currently have a long-term duplex in Wisconsin.

Hopefully, not an expensive tenant or Fair Housing lawsuit.100% of what @Travis Biziorek states is true, but he left out a key fact - he lived in the Detroit area when he started investing here, so was able to self-manage and meet everyone he had to hire face-to-face.

If I were investing in eastern WA, or where my extended family lives in Pennsylvania, those 100k houses in good condition are a real thing there.  

Quote from @Roxanne Whitaker: Please be aware if you buy an investment property and do not live in MD, when you go to sell it you will pay an 8% tax at settlement. 

When you sign almost all mortgage closing packages, you are signing an Occupancy Clause that states you are intending to live in the home for 12 months.  

I'd recommend house-hacking a duplex or triplex if possible to help limit your living expenses.

FHA loans require living in the home as your primary residence for 1 year after purchase.