How long is a piece of string?
So many variations that come in to it. Free standing or attached, local building codes (cyclone coding here and you wouldn't believe what that adds to cost), does it intrude on building setback regulations and may require Planning approval and/or you have a Neighbour that might object to some aspect of it, Owner Builder or paying someone to do it.
Edited: Just thinking that I might have sounded a bit negative. Not intended. Location you are in unknown but is important. I've taken the easy wayout, most expensive, twice, and for what I got you could probably have gotten a much bigger carport done in most Southern places. Local building regs for cyclone coding add so much and then there's the local labour costs. The more lightly built type of structure that is acceptable across much of Australia could be a 1/3 of the cost. You could well get a kit that you could do yourself but then have to deal with Councils etc to process it. It can be so much easier to just contract some else who takes the stress out of it.
