Why open your own shop when you don't yet have the sales to back up the overhead & inventory? In my experience (10 years in my business so far), product is cheap & plentiful. Folks can get it anywhere and good product makers are a dime a dozen. What makes businesses successful is sales. You can have a rotten product that you push like crazy and sell it hard and make out like a bandit. But the inverse is not true -- you can have an awesome product with little sales and you'll be yet one more small business statistic. Obviously, having both is best. But sales are clearly the leading indicator of success, not product. I hate this reality and still focus my business on good "product" (service business) but I also know that I can only do that because I spent 3 years knocking on doors every day to drum up the customers I needed to eventually run the business I wanted to have. But for all those years, I watched my colleagues and competitors make a ton of money offering vastly inferior product/service, win awards, get bonuses, etc. Their customers don't know any better and even if you told them, they wouldn't believe you because they're sold. So instead of asking about inventory, consider looking to team up with a few other shops to work on selling whatever will sell. If your dad has a compound shop, work that connection to access that customer base & sell it hard. Find some vendors that will allow you to have some free demo models on-hand to put in the hands of prospective customers or start an Amazon drop-ship business for stuff that sells everywhere, using your website as a marketing channel for other people's products. Private label another business's product. Work with outfitters, coaches, etc. to access their customers. Lots of options here but the point is to focus on driving sales first, then worry about how or exactly what product to carry. Once you have the sales coming in, you can negotiate with product providers for discounts (increasing your margins) or allow other vendors to access YOUR customer base to sell their stuff. Sales are the biggest challenge of any small business, hands down. Figure that one out first before committing too hard with your time and money.
But like all free business advice on an internet forum, it's probably worth every penny that you paid for it. I don't think myself any exception to that rule. It would make me very happy to be proven wrong and I sincerely wish you all the best in business.