In the 70s I had a couple of partners in a shop business.I was the the welding and fab side ,one partner the parts guy and the other was an excelent Case mechanic.We had a lot of Case construction equipment in our area but no dealer representation. We aproached Case for parts support with no luck,but persisted with them and able to become a Case Ag dealer which gave a backdoor into the parts . The construction side was successful but in the end those darn farm tractors buried us and Case was too bullheaded to allow us a straight construction dealership. Big OEM manufacturers are pretty complex for us average tradesmen to deal with. Id stick with picking the best of manufacturers ,and starting with good used stuff.Just remember product support,repairs and delivery are the key. Keep an eye on your local market and see whats needed . One of the most successful rental houses in my area has been around for ages and resisted takeovers from the big guys im sure. They are specialists in odd stuff for mill and industrial . Lots of heavy rigging ,air tuggers chain blocks ,big portopowers big air tools of all sorts as well as the standard items for the public. Good luck with your venture .