Are those "we buy houses" businesses legit?

not hitting the panic ons yet but would love to get rid of this house (actually its half a duplex, fairly new (built 2006)) by early november. the sooner the better. Ive already paid off 20% of the purchased price/ mkt value. appraised value went up about $1000 since purchase. pretty much stable. thinking about just settling in for the balance. will these type businesses settle for 80% (basically a discount of 20%). renting is not an option, just want to move on (getting rid of because of job transfer) with no burdens. any good suggestions/ strategies to sale, get rid of house quickly