I just grind Trash Talk and grab a gang peyote to sell from the vagos turf while doing it, they won't attack you during the mission and you can't get a bounty. Mission pays 23k ish if you take long enough getting the car and peyote sells for 12k. Its not that profitable and gets mind numbingly boring though.
I sold my T20 as I don't really like it any more, I much prefer the Osiris. I bought an Adder with the cash and upgraded my Sabre Custom a bit. The Adder has become so rare and that's why I like it, every motherfucker has a T20. It's the same reason I sold my Zentorno long ago, although the Zentorno is ugly as fuck too which was good enough reason for getting rid of it.
Also if you're on PS4 the community on here is fairly active, sure someone will join you for heists etc.