The literally single biggest mistake that people make is to buy a class D property, because it was cheap to begin with, 90+ days on market and they were able to negotiate a "discount" - ask them a year later how that worked out for them. 

When I first got started, I made a huge mistake by skipping this step.

I'm 20 and this'll be my 1st buy and hold so don't want to make any rookie mistakes.

That fact alone rules out Florida.The biggest mistake we see investors make is blindly investing and not understanding what is going on with their properties.

The reason I'm asking is because I made so many mistakes on my first property and I made them because I didn't ask enough questions.

That is a good point, and when I think of what makes me feel more confident in my first flip, it always has to do with mistakes around the rehab (cost miscalculated and time lines)  

My jaw dropped to the floor.LO at a big bank researched this extensively but concluded that this was not a mistake.

Mistakes that cost a lot of money can happen when you're feeling emotional.

We made the mistake of thinking the person who charged less was the better option, however in the long run we spent more.

Buying properties in such locations is a fatal mistake.