I had a 7 Mx7 M carport built, using 4x4" steel posts with footing, only 2 posts as otherside attached to house. Labor was 25,000thb and they primed all steel and total cost was 47,000thb. I bought all materials. No cement.
I just recently got a labor estimate for a 3x7M shade, 350 thb/sq M. No cement, again I'm using 4x4" steel posts with a footing.
Mine has a 7 M span both ways, the less posts you have the easier parking you'll have, 15 M span you can get by with 3 on each side. The good roofing with the inside insulation cost 150thb/M 3 yrs ago.