Greenhouse question

I was thinking of building a simple greenhouse for next season, something like a wooden frame with plastic on the outside, it'll stand about 5'-6' high, and be about 4'x4' around. The main point of the greenhouse will be for concealment, but I was wondering a few things first;

-would this have any impact on the way the plant grows?

-would I need to water it more often as the temperatures will probably be increased?

-do you think the 5'-6' , 4'x4' will be enough room for one, maybe two plants? (know any specific sativa strains that would work well with that area?)

Thanks for your help!

A sativa will need trained or trimmed back to keep her down to 5-6 feet. You may be better off with a hybrid...and a single plant in 4x4. Vents to keep the heat down.

Howbout the humidity? Temps around here usually reach 85F-100F mid summer, really low moisture amounts though, so I didn't think it would be an issue, the only thing that might affect it any different is the plastic, anyone have any info on this?

Thanks again!