Just pick any android released like 2-6 years ago, look on eBay/plebian.market/satscrap/shopstr, and there it is used for like $50. There are linux distributions for android that are full linux distros, or you can stick with a normal android ROM. I haven't researched it in a while, so I don't have any more specific suggestions, just saying it's maybe an easier path than doing this w pi. There are ways to run python etc even on an android rom.