What happens to used components when a system is replaced? If I need a large, centrifugal fan for a project, is it worth asking a local HVAC contractor?

I'm thinking of building a small-ish wind tunnel in my garage for some experiments. I don't have a huge budget and was trying to think of ways to get a centrifugal (preferably) fan that can move a large volume of air. Greater than 3000 CFM would be ideal.

However, I'm just in the very beginning research phase and am trying to figure out if this is even something I can do on a budget.

My core questions are:

- Do HVAC contractors keep parts from used systems at all?

- Can you buy used blowers from them?

- Is 3000+ CFM an unreasonable thing to look for?