Seven years ago when I ventured into this hobby, there were a decent amount of project machine available through different avenues. Craigslist, auctions, word of mouth & even yard sales were the means to pick up a project machine at a reasonable price.
I would acquire a machine(s) & fix, shop, then flip for a profit. For example, I put a bid of $500 on a roached Centaur at an auction & expended another $600 on a very nice restore job. Flipped it for $3800 & the buyer was completely satisfied. This went on w/ many-many other machines, but within the last year or so the pin deals have completely dried up.
This approach has allowed my wife & I an arcade in the front of the house & a few pins in the back of the house. We are very fortunate, as I consider pinball escapism at its finest ~ especially when combined w/ beer!