Vinyl is a slippery slope - I know , as I am currently careening down it at somewhat out of control speeds. I have both digital and analog going now and still buy both formats. I love my vinyl obsession, but it is much more expensive than digital as it is easy to get seduced into upgradeitis.
When I started buying vinyl, I was very wary of used and only bought new - mostly reissues. With a lot of research online, I was able to identify the best quality recordings (thanks Steve Hoffman forums) and the best prices. Nonetheless, I have bought almost 600 albums in the past year at a cost of over $8 grand. Probably 10% of these were used.
In the case of used, I found that there were a few shops in my area that were good places to find clean copies at fair prices, but these still cost $6-$12 depending on condition, vs $12-$18 for new on sale. ( I have spent as much as $40 for a single new album - but these are the "audiophile" editions that guys like Michael Fremer rave about). Occasionally I have come across great buys in the $2-$3 range, but it is very dependent on the music you are looking for. FWIW - my entire collection is almost entirely comprised of albums originally recorded before 1980 (pre digital), or some recent albums that are largely or completely analogue recording / mastering (i.e Vanessa Fernandez - thanks Mr. Fremer).
During that time I also bought CD's, including several SACD's, and typically spend $4-$6 each (SACD's $10-$15). I am careful to read up on the mastering quality of these as many are not well done. I have over 500 CD's, mostly purchased in the 80's and 90's, and many are unlistenable on my system - overly loud and shrill compared to my recent purchases.
Bottom line - my experience has led me to conclude that, to put together a good vinyl system ( TT, cartridge preamp) and a decent album collection is at least a $1,500-$2,000 investment, and can quickly grow from there.
If I were on a tight budget, I would probably stick with a laptop as a source and a good DAC. There are plenty of online sources for lossless or hi res files cheap or free.
