It is not necessarilly a money thing. It takes a great deal of time & effort to track down the myriad of parts you need to make a bad car anywhere near good.
I mean, price a pair of seats & then add up the money for however many bits of interior plastic you want to replace. Thats easilly $1k there. You can do a similar exercise for tired suspension, paintwork, brakes, drivetrain & yes even the engine. Before too long the car will be costing you more than the really nice example you thought you couldn't afford in the first place.
With regard to the engine, just get it checked. There are loads of threads about what to look for.
And lastly, don't take too much notice of the (mostly GTS-T owning) doom sayers who will tell you it will cost more to rebuild the motor than the national debt. There are many, many owner who have never rebuilt their RB26's. I'va had four, never lifted the lid on one of them.