Welding and Metalworking - Steel Beams

I am building a barn and I am going to need a beam that is 55' long. However I want the front 15' to be an overhang without a post. There will be two beams down the sides of the center portion and then the two sections on the sides will have roof jacks running from the outside walls to these steel beams down the middle. It will have a gable roof on it. I am wanting to put a post in the back, another at 27.5' and another at 40' in order to give me that 15' overhang. What type of steel and size do I need to use for this? The only dead load will be the weight of the roof (metal panels), live loads may include some tree branches, up to 2" of snow (doubtful were in Houston), and some typical barn equipment like ropes, wheel barrows and things like that. Please help, I need to build buy these asap as I am trying to rebuild from hurricane Ike.

http://www.ou.edu/class/hgruenwald/teach/4333/4333l14.htm

I would suggest having an engineer design this for you. Not only is it the better way to do it, it may be required for the building inspector anyway. Whenever you engineer your own structure, in many areas you have to have the engineering specs to back up the design.

I agree that sizing the supports for your building is not a diy endeavor.
The overhang you propose will need extra deep footings on that support column because of the extra forces placed on it by the cantilever.