Do you mean as a contractor?

If so, how normal is it to go through an interview process for contracting? I got friends who told me they had to interview like for a regular position even though they're contracting, but I should say that those I've heard it from are contracting exclusively full-time for a single company. So how normal is it for 3 or 6 months contracting?

I am not sure. I've never interviewed for a contract to hire job. However among those I've worked with who were in such arrangements, the bar to hiring was lower.

Sure, and those of us that are decent and have fte with real benefits aren't going to take a 6 month contract in hopes that:

A. I'm a great fit for your after hours drinking club. B. The headcount still (or ever existed) for my fte position in 6 months.

If you want a lower threshold for being hired, you have to accept a higher risk of being fired. If are established in your career then by all means don't take a contract job. But they can be gateways to a first job for many people.