Hi Vroom and Welcome!

My advice. You can't get any 250cc bike worth a shit for 15,000 new. If you find one it will be a brightly polished China-bike turd.

However your best bet, and damn it won't be easy is to find a used/plated and hopefully insured Yamaha YBR250 put a road/trail tire on the front or both ends with the official luggage racks you kind find on Taobao, then optional hand guards, gators and home brew a sump guard. Alternatively just buy a new YBR250 and do that.

Or buy a Sundiro Honda CBF150 and kit it out or buy a YBR125G or K or whatever it's called.

I'm not saying no 'China bike ever' in fact I think a Jialing JH600 would be a great bike for you, but it might be a little over budget, but damn I'd stretch for one if you find a 2nd hand one.