So what are you really looking for towards turbo setup?
There's ebay kits for 800$ and name brands for 7000$

Obviously it depends on your goals, but I'm looking for ~350HP with small boost on built h22a.

Realistically, how much would a decent, reliable turbo setup for low boost cost? What should I look for?

 

The FAQs for starters.

 

do your research and put a used kit together. you can do it easily under $1000

 

google, faqs, all the above

 

$3K on average, not including good tuning and tuning equipment

 

Where would I look for used turbo parts? Forums?

 

For starters. I predict you won't get past the Q&A stage. OR you buy a cheap Ebay kit and blow something up.

 

Just the fact that your asking for advice on what to use on a "BUILT" motor suggests to me you should hold off on going turbo until you speak to a few tuners..actually go in and ask them what you would be looking at to go turbo.....there are thousands of these types of threads with answers to every question you have.