Estate pipes are a good way to go, once you've established yourself a rotation.
Why after, you might ask...
Not only might it take a bit of work to refurbish, which may take a bit of time... but it may not be a great pipe for you afterwards. It may be awesome, but like with any pipe, you take a chance.
Why a greater chance of failure with an estate pipe?
Aside from the obvious reason being condition, you have to consider what was smoked in the pipe before. If the guy smoked nothing but nasty wet Walgreen's Cherry tobacco... it's gonna be hard to get that taste outta there. If he only smoked english blends, i'd be happy with the pipe, most likely.
Another thing about eBay, is it's a "dumping ground" for pipes that don't smoke well, or to someone's liking. Question is if your opinion is different... but odds are that the pipe does not smoke great.
Therefore i feel it's best to get a rotation into place before experimenting too much... you don't want to fill up with rough pipes. Your goal should be a quality tool that allows you to taste your blends, best as possible. New pipes IMO make that goal simple.
Ebay is a good place to find estates, but the worst way to buy them. You gotta be really carefull. I bought a couple estate pipes from Tedski, and i could'nt be happier with em... but i doubt he'd sell anyone a piece of crap.
Theres a few websites who specialize in estates, and i'd rather spend an extra $20 on a refurbished pipe... and know there won't be a hole burned outta the side of it, or crack in the shank.
In contrast, i found a guy selling old, but unsmoked pipes, on eBay. I ended up with a few for about $5 each. They are not high end, but styles that i like, and nice briar. One was a Calabresi which i really like... that one alone was worth the price i paid for all of them.
If not for that score, i would have gone to Tinder Box, a local store, where i found nice pipes at fair prices, and i would have bought some pipes in the $30-$40 range. New, i can break em in carefully, and have a good starting lineup. Even $10 basket pipes can be a good beginning.
After you have some experience, chancing $10-$20 on eBay estates, can likely get you some real deals on fine pipes... but you'll also find alot of competition out there. I'd be real carefull about bidding more than $20. Get some opinions from guys like Tedski or Sgresso first.