Typically a bedroom can not be a "legal bedroom" without a window. Older homes window sizes may be smaller then today's standard bedroom windows. Look up the National Building Code guides - BOCA referred as.
The correct size today for a bedroom window really has to accomodate a firemen dressed in full gear - different if a doublehung (slide up and down) vs a casement window.
In general, basement apartments, with only a "basement" window 4 from the ground are illegal, but you see them everywhere.
In many towns in the us, a rental unit must be inspected and issued a certificate of occupancy. Not everywhere, but it should. Also, you should check for smoke detectors and in case of a fire at your front door - how will get out - or will you die stuck against a wall?
These are the pitfalls of renting and landlording. Be careful and Be safe.