Not a vet, but the advice I've heard is to buy used up front for the low and then you can increase your spending if you really get a feel for things and want to take things further. I would use Facebook Marketplace or OfferUp and then cross-reference the model on Amazon to make sure it is well-liked (4.5 stars minimum) and popular (+1,000 ratings). That way, if you like it, you can buy additional parts easily, and if you don't like it, you can still flip it and get most of your $$$ back.
In terms of photo editing, I have GIMP on my PC since it's free but that is more because it is open source than because I've been actually using it, so I can't offer you any advice there.