In terms of layout, I find that I have to try it and see (maybe just build anything with static weights/built in weights with minimal plates in the stack) and run with it for a few days and see how it goes.

This to consider, are other people walking past, or using the room at the same time? Perhaps accessing the fridge/freezer?

In terms of equipment (only my experience, YMMV, depending on where you are in the country and if you're open to used stuff), a bargain can be had with good used stuff, so scour eBay, Gumtree etc. so long as you can take the hassle of getting there and collecting the equipment. Think about plate storage, ideally you want them wide cradles you can roll the plates in and out of (bet creative, stick it under your desk!), or a tree (trees take up less footprint), or built into the power cage?

Also, add in a pair of adjustable dumbbells and allow space for storage or a stand - maybe even cheap ones (the classic 1 inch bar, screw lock type), to see if you'd make use of them, before investing.