nice set of lenses to inherit
i'd +1 on K-01, K-50, and anything else with focus peaking for that matter. it's really a must-have feature for me. while the K-5 and K10d discussed are good cameras, i never warmed up to focusing on an APS-C camera, even with focus aids. the viewfinder isn't as bright as a film camera.
a used k-01 could probably be had for $200-$250 and a used k-50 was sitting in the marketplace here for $250 i think, but has now been sold. i'd look at the sold listings on ebay and here to look for current going prices and have some patience (i usually overpay because i'm impatient). the k-50 would be the better bet because if you don't like focusing on the screen, there's the viewfinder too. and it's weather resistant! and faster than the k-01 i believe. if you get a k-01, just realize that it's a mirrorless, but it's not a mirrorless. since it still has the K mount and not a new mount, it still has to have a large body. it's a mirrorless disguised in a dslr body sans mirror box