How do you get multiple mortgages without hurting credit?

[Nicholas Layton]

About 2 years ago my brother convinced me to stop renting and start owning, so I bought myself a condo. At the time all my debt was a student loan, and a car loan. Once I got my first mortgage my credit score shot up 63 points. Last year I paid off my car loan and that made me lose about 10 points. Life happened. I needed to move into a house. This year I bought a house. My 2nd mortgage dropped my credit score by 63 points. My condo was 100% owner occupied so I couldn't keep it as a rental, I had to get rid of it. When I sold it, paying off that loan, dropping my total debt, lowering my debt to income ratio, moving from 2 mortgages to 1, only increased my credit score by 1 point.

I will NEVER under how credit scores work, but I know they affect chances of getting a mortgage and interest rates you can get. I can only imagine if I buy another property for a rental it's just going to punish my credit score again even more, so how do people do crazy stuff like buying 18 properties in 18 months with completely demolishing their credit scores?