Any bicycle experts out there ?

[faraway]

A used one for $100 sounds good. A new one should be more expensive to be robust. You should have an eye on the tires. They should be a compromise between very slim racing type (fast) and very wide (comfort). Have also an eye on the weight if you have to up hills. For casual driving is 5 speed perfect. The more speed the more likely is a defect.
Drive save and have lots of fun!