mostly good advice so far... idont fully agree with the ego comment but I see the point DVS is trying to make.
I think if you are using one almost every week for similar tasks then its time to buy. However unless you can afford the payment of a new one...which are typically overpriced....then it can be a painstaking process to find a good deal on a quality used machine that fits within whatever parameters you have.
I searched for almost two years before i purchased my gently used CAT 304. I ended up paying nearly half of the cost of a new one and it was/is just like new.
Same for our 257 we have...i drove to KENTUCKY for the right deal after looking for a year.
I would have to say If I were you I would give yourself another 6 months or year to look and save save save so you can spend at least 25-35k and you should be able to find something quality.