My eventual plan is to have 500 blog sites going on all different niches but eventually I just want to leave them and earn money without having to update posts. Most of these blogs will be 10 posts. For example, a vacation blog site with a list of top 10 vacation hot spots with a small review for each of them which consists of my unique keywords. So, do I have to keep updating the content, or is keeping up date on my links enough to keep my site ranked well?
If there is no new content googlebot will visit less frequently. If googlebot detects that the blog is never changing then it doesn't matter how many great backlinks you have, it will mean that googlebot arrives, checks content, sees no update and leaves. The site will drop and continue to drop out of the SERPs
I think it's best to manage good 4 , 5 blogs than managing 500 blogs you surely will if you go practicaly through this because it is hard to maintain 500 blogs by single persone