First time I've posted on /p/, got some general questions which are probably retarded but here goes

I'm near completely new to photography and have spent the last week reading up on the technology and composition, etc.

I've decided to start as a hobby and I'm interested particularly in shooting blue hour, twilight and morning/night photos, even moon photography. I'm also likely to shoot urban/street stuff, also with a focus on blue hour. I'm also situated in a really great country for landscape stuff.

Since I'm completely new I'm looking to keep my budget low and the Nikon D200 and D90s are available on ebay for as little as £40 and £100 respectively.

BUT I'm also looking for something I can forget about and use for 10+ years. I'm also very aware mirrorless is probably the future and I've been looking at the Sony a6000 which goes on ebay for around £250

What's my best choice? What else should I consider? Where am I being a noob? Should I buy more than one body?