One thing you can try out for storage is buying regular 2.5" solid state drives (the kind you install in a computer) and using a SATA to USB adapter to plug it in. It’s probably less durable than a proper external SSD, but gives you a path forward if you later want to install them into some kind of network storage server (or have a friend do it, if you’re not sure how).
I haven’t checked the prices very thoroughly, but you might be able to get the internal hard drives for cheaper as well. If you’re willing to go with magnetic drives (3.5" HDDs), you can get bulk storage for (relatively) dirt cheap, of course at the cost of having a noisy drive spinning up each time you open a file on it.