Order of operations

I've been thinking about the Painted Smiles remake I want to do. A question of logistics comes up - should I start recording the instrumental tracks as soon as I have the funds available to pay the studio fees, or should I wait until I've found a vocalist first?

Normally what I do is record the instruments first, then add the vocal layers on top of that. That's how I normally work - so why should I consider changing my methodology this time? Because I might want to record the song in a different key signature based on the range of the vocalist I find, that's why.

So do I wait until I've chosen a vocalist and record the tracks in a key that works best for him? Or do I make it a requirement that the vocalist be able to perform the song in the key in which I've written it?

I don't know yet. What process will I use to decide? I don't know that yet either.