Hi Maree
Like the others said, something is worth what someone is willing to pay, so you stop thinking about the purchase price if you love it, because that is the cheap bit
It's good to not go into these things in a rush, don't put too much of a time limit on it as this like anything in life will only detract from the whole experience, plus if your bro is going to do a lot of it with you, make sure you go at his pace and don't rush it.
I have done up cars b4 and rushed and taken short cuts and afterwards u end up thinking "i wish i did this or that better when the car was apart".
I am planning this one very carefully (my FE with FB30), as FC Hoon has said to me and I agree, try to think ahead a bit and make difficult ( or what may seem to be) changes to suit possible future alterations, like if you want a bigger motor and don't wanna do it yet, you may as well do those little upgrades like wipers and brakes while everything is out....just think ahead a bit if its a long term car you will keep. I am at about same stage as you b ut have started a month ago.
For instance I might do a stock RB30 to start with but will probably put in a heavier rear driveline if I plan the same running gear. If I was gunna go v8 later, then id probably spit a few diffs and go with what I got now because I'd have to do different gearbox and tailshaft anyway etc.
Going V8 adds a whole new ball game, heavy engine requires good front end and chassis setup versus a straight six or v6 etc etc...
Cheers and good luck.
Deano.