Generally we've moved on and 90s bikes that are more modern are better bargains.
hi-ten 'high tensile' 'gaspipe' steel is the worst you can get. It's very heavy, and doesn't flex nicely. Better steel will be butted, meaning the tubes vary in thickness, which makes it lighter and ride better. Look for chromoly and butted. Good steel tubeset makers include, reynolds, columbus, tange, ishitawa & true temper.
Only really cheap bikes came with dual brake levers, that you can operate from the tops of the bars as well 'suicide levers'. Nice bikes also have rubber hoods around the brake levers, not bare metal.
Only really cheap bikes came with stem shifters, look for downtube shifters, barends, or integrated shifters.
Nicer bikes generally have 700c wheels, not 27". There are fuck all tires available for 27" wheels. Chromed rims are steel rims, only found on shitty bikes. You want aluminium rims. Steel rims will barely brake in the wet.
Bikes with kickstands are almost all shitty.
Cottered cranks are absolutely terrible, huge red flag and endless nightmare of creaking.
On cheap frames, the rear derailer has a claw that bolts onto the axle, rather than threading into an integrated derailer hanger on the frame. That's the biggest tell for a cheap bike.
Atleast it's probably in good condition. If you had no other choice, and it was $50 then you've got nothing really to lose i guess.
It is shit though.