Hi Sebastiaan, If you like to start a new business you should always start small. I suggest you start with a website/shop and start learning which products have a high demand. You’ll find out soon enough which products need more stock and you also learn if your business model is viable/scalable.
As soon as you can’t manage your inventory and orders/sales on paper anymore you should start looking for software. We recently started a cloud based rental software company called Booqable Rental Software. Have a look as soon as you’re ready. We started allot of other (successful) companies and love to help you out 🙂