Advice on building a deck

Hello,

I am building a deck, 250 sq ft with no railings and stairs or anything, just a simple n plain deck, basically 2 feet above the ground so it's level to the backyard door.

Can you guys please tell me how many posts are required, how many beams, and how many joists?

How much would a contractor charge for everything?

Or how much would a contractor charge if I buy all the material and charge just for labour, in Mississauga, Ontario?

I know its alot of questions but it's my first time and I am just curious. Would appreciate any help I can get.

Thank you in advance,

John.