IS it OK for a 21 years old to date a 18 year old in Maryland

Yes. Why wouldn't it be okay for two adults to date? What is scary about it?

However, just because they can doesn't mean they have enough in common to build a viable relationship. Another factor would be if the 18 year old is still living in his/her parents' home. Then they may have house rules that might affect the relationship.

Legally it's ok...why is it scary?

I can't see how you would have much in common... there is a huge maturity difference between 21 and 18. But as was stated... if she is still living at home... she's got rules to follow... and I doubt at 18 she has her own place and is supporting herself.

I'm assuming the 18 year old is a she.... if SHE is the 21 year old...I really have to wonder because females mature faster than guys do and that maturity gap will be far wider between a 21 year old female and an 18 year old guy than if its vice-versa

But no it doesn't make you a pedophille.