If I was starting out with $6k, and could find those two for $6k combined, that's likely what I would do.

for $6k, starting out, you can get:
Congo $2500
Eight Ball Deluxe LE $1500 for a nice one
One System 11 like Pinbot, High Speed, F14, etc. for around $1000
A couple EMs or or an EM and random early SS Bally. for the last $1000.

5 great games for $6k.

If they're in good shape and fully functional, I think those are nice prices; I would've guessed those two go for at least $2k each unshopped, and probably closer to $2500 each in fully working shape.

Not particularly great games, though. Not bad, but there are far better games out there for $2000 each. Good used Sterns seem to start around $2500-3000 (Ripley's) whereas $2k buys a lot of the better-playing Bally/Williams DMD titles.

That said, if you can get a Pinsider to check out those two for you and they're clean, you can probably play them for a year and trade them for other titles down the line pretty easily.