What is the size and weight limits for bags for carry on and under plane? How many can I have before it is extra costs?

Check with airline.

Agree with Pamela. We did alot of research before flying. Baggage sizes and rules were dependent on which airline we took.

It's best to Google the question as this may vary by Airline. Generally, 1 checked bag with weight restriction and one carry-on which has size & weight restrictions.