Best of luck to you, that's not an easy venture these days.
I suggest reading Tony Avent's book, "So you want to start a nursery", which has a lot of good information in it.
Different and exotic seems to be a niche business, so I suggest having some of the usual boring stuff (LOL) as well. I love any plant that's different or unusual, and many of the online nurseries that specialized in them have gone out of business, I've also known people that have tried to start an exotic nursery and failed for lack of customers. You and your mom seem to have good experience, which is great!
Sign up for business gardening magazines like Greenhouse Grower, Green Profit, and Grower Talks. Good information, and a classified ad section where you might find equipment. I think Poly-Tex is in MN so you might look to them for equipment, freight costs would be lower.
You might also think about having a landscaping division down the road, or partner with a landscaper/designer. Start up costs are probably high, but it can be very profitable.