I am wanting to build and/or buy and 26 or 29er.
I dont have alot of moeny to put up for this (16 and work like 28 hours a week)
I have and older 24" but i am wanting something a little more off-road like:)
so if anyone now were to get cheap parts to build or buy one,or ig even turning my 24" in to more of an off-roader.
thanks
Your best bet is probably to buy something. This is easy to do if you are patient. Let the money build up. At 28 hrs/week, this shouldn’t take too long unless you have to pay rent or buy food. 
Building your own it’s pretty hard to come in cheaper than what’s on the market. And turning the old Schwinn into a 26" doesn’t work well either; you’d be starting with an inferior platform. The best you would get would be something inferior to the cheapest 26" on the market.
You could check out eBay for used unicycles, but most of the cheap ones are low-end 20" and 24" unicycles like the one you already have. You could find something though; there or in the Trading Post here…
Id say you do! In the UK its 3.57 minimum for 16 yr olds. So thats £100 a week!
Assuming it works out pretty similar in the US, just wait 5 weeks and you got yourself a 26" KH! Wait less time and you could get a nimbus or something 
Although if you have expenses it could take longer.
Alternatively your best bet is to lurk in the trading post for a while and your bound to find a deal eventually.