I happily used a blade grinder for years before I upgraded. As others mentioned, you can get into this hobby without spending a lot of money (my current grinder is a commercial unit I bought used for way less than $170).

However, as long as you have an oven (and don't live in the immediate vicinity of a local roaster), you'll find that the DIY roasting route gives you 90-110% of the benefit that you get from buying online boutique roasts for store bought prices.

And let's be honest, this is one of those hobbies (like drones, 3d printers, or photography) where you'll eventually find yourself wanting more than a french press and hand grinder.