Last year I bought two 2000 boxsters and got the deferred maintenance up to date, some of the story is in these threads.
Into Boxsters with both feet... a green one and a blue one.
My Blue Boxster refurb.
I spent about $1300+ CDN on each car for maintenance (oil, filters, coolant, and all sorts of missing bolts and doodads including things that got broken during disassembly), getting a second key (close to $200), tires for the green one and a clutch and drive shaft boots/rebuild on the blue one. I do all my own work so there is no labour in that figure. I try to use used parts where possible and only do what has to be done.
Both cars are running well and can be enjoyed right now, but both have other things to do like changing the transmission oil, probably engine mounts and eventually cam chain tensioners (especially on the blue one).
So count on $1000 US and some work over the short and medium term just to get it up to snuff. But you will be rewarded with a great little ride!