Brian, I can't help you with the best price or financing, not even recommend a company. But I will give you a heads up on some other issues I do know about. Just becasue a company has sold a gazillion buildings of the same design, does not mean it will meet code for your location. make sure the drawings will pass the building department before purchasing any building package. Be very leery of the great deals that many companies offer. they are usually deals that fell through because another customer ordered it and then learned it does not meet code. An example that I know of is a great deal a neighbor got on a garage only to find out that all the bolts for the entire building did not meet code because of the winds in our area. He had to go buy some $5000 in bolts to meet code. To find out your entire building is not made of heavy enough steel would be a real tragedy. I simply suggest that any contract you sign is on the contingency that the building as is passes the building departments approval or the company corrects the problems at their expense. In other words the contract is for a building erected, in place and usable not just the parts.
Another tip is if you see a building that you like, ask the owners of it where they got it.