Work Computer build.

I am on a bit of a budget and looking to build a work computer that I can continue to update as time goes on. What would be some recommended builds for under $1.5k. It could be cool to host my own servers/Internet down the line. There are also A LOT of desktops for sale locally. Perhaps I pick one of those up and build off of it? They are in the $500 price range and will comment builds below. Thank you all for the assistance getting me started!