A good centennial with good decals will bring $400.00 with case. A good FW without case can bring $300.00.
You can buy a new FW case for around $80.00. Don't actually need a FW case. A lot of other small hard or soft
cases will work. Main thing to check is that you have a strong motor. Other issues aren't hard to fix.
You may be looking a long time to find a cheap one that you don't have to put money into. They are just too popular.