Hi dude I was in the same boat as you last year, worked for a local company for 6 years then went freelance and didn't have gear!
I looked at a lot of options and went with the 664, it just had everything I needed. yeah I took a big hit in the pocket but I've got it now, finger crossed ill get a decade hopefully more out of it! I went with a couple of G3's with 4071's and can't complain, yeah there not 2020 but they do the job on Doc's!
Secondhand gear can be great, 552 or Sqn 5 great kit and if your going straight into camera all the time perfect, but they are still over £2000, then throw a recorder on up either buying or having to rent one every time u need it, overall your not far away from a 664 price tag!
Or a nomad with the option of upgrading it, thou u'd need to look into that one! But it's another great kit with all the things ull need!
future proofed I think it's called! Well as future proofed as you can be...