Matt,
Welcome, I joined a few months ago and this site has been very helpful, it’s a great place to learn from those who have experience on what does and doesn’t work.
My advice, for what it is worth, is buy the best car you can afford unless you have the skills and circumstances to buy a project.
I made that mistake with a 1 owner BMW motorcycle a few years ago, the owner had got too old to ride and pushed it into his shed and left it there for the next 15 yrs. it was totally original and had 33k miles on the clock. I paid £600 for it. 5 years and £5k later I sold it. The whole experience was a nightmare because I don’t have the skills and had to employ those that did (not always very successfully).
Whatever you choose to do, all the best with your search and enjoy the Z