It's shenanigans, all the way down.
Permanency is full of them. In particular, it's almost not possible to balance Permanency completely. As it is, in 5e, high-level wizards (and other casters to a lesser degree) get some entertaining things that they can do to abuse the system for significant permanent beneficial effects, generally restricted to spell level 6+ (the level when you can start socking clones away to achieve immortality). Permanency, in whatever formalformat, is nearly the most perfect form of this.
4th ed, the edition most obsessively tuned to prevent over-time accumulations of this kind, eliminated Permanency entirely. 3rd and 3.5, which were nearly the most open in letting people come up with fascinating new ways to break the system in such ways, still limited the kinds of spells you could make permanent to a specific list, and had it require the investment of permanent resources in the form of exp. 5th ed hasn't added permanency at all, in spite of it being iconic, and in spite of them having a focus on bringing back many of the iconic things that 4th ed dispensed with.
More to the point, 5th ed has the concentration mechanic, which generally limits ongoing spells to one per caster at any given time. Currently, in-game, there is no way for a PC caster to have more than one spell under concentration. There are no races that can do it, there are no feats that can do it, there are no class features that can do it. There's a clear attempt here to make the concentration limitation a big part of balancing spellcasters, and Permanency basically takes that balance and shatters it.
So... so far as I can see, there really is no way to balance this one. You'll either make it nearly unusable, completely balance-breaking, or both. If the designers could have come up with a version that didn't break everything, it seems likely that they would have, and it breaks many of the current balance assumptions. This is something that a few of the very-high-level spells are allowed to do to a degree (Hi, Wish! Hi True Polymorph!) but even there it's done with some pretty stark limitations (...bye, wish.)
Now, if what you want to do is significantly crank up the level of shenanigans available to your wizard, then you could maybe try to design the spell around that. Permanent magic effects could conceivably be balanced against major magical items. The attunement slot cost is a good start there, though it should be specifically on the target, rather than the caster. Still, even that would take quite a lot of work to make non-game-breaking, because "material component, plus days, plus can cast this spell" results in a radically different level of effect than "magic item, attainable at this level". It might work with some sort of a 3rd-ed-esque "list of acceptable spells", curated carefully. Regardless, the version you have there is definitely exploitable.
