3,000# and 5,000# propane with triplex masts to start off with.Ratio of 3 to 2 with the majority being the 5,000. Maybe an electric as well. As people have said the big guys are going to look at you and say so what?
When I was with a company and we were starting up like you we did 24/7 service availability. Paid the mechanic to take the cell phone home and answer it during his 12 hours. Not many people called but those who did were very grateful and very appreciative to talk about their problem,which they fixed on Monday at regular rates. It was a great sales tool for us and made people sit up and notice us. We literally stumbled into our largest rentors the docks and peanut processors. After some time it then gave us a good well maintained used truck inventory to sell.
Good luck but forget all the pre-conceived notions, pick a sales hook to get people interested and start getting the flyers out and see what develops.