That's a 2014-ish Mongoose Sector, which is low-end but not total ahite. Sold at Halfords UK for £329-399.
It has an Altus derailleur which is a step and a half above the non-group derailleurs and a step above Tourney. Probably a low-end coil spring fork, which aren't the nicest but usually require less maintenance than air forks.
I wouldn't pay any more than $40 USD.
Last edited by LesterOfPuppets; 01-01-21 at 06:55 PM.