My 2 cents
I had similar symptoms with my battery. It looked good after being on the charger, engine turned over a few times then would not.
I replaced the battery, charged it over night and all is good.
I would suggest
1) Do as the previous owner id and jump start it. If that works - you may have battery issues
2) Ride it to Autozone or one of those places and have them test the battery.
If it will not jump start - then could be a wiring issue with something grounding out , but then TuneEcu *may* throw an error code telling you what is disconnected.
Sorry if this does not help, but I wasted a lot of time suspecting R/R, Stator etc and it was my battery.
Dave (in Dallas, TX.)