I had the idea to make a warlock, that involves paying money to your patron/accruing wealth for them. I think it would involve abilities like trading gold for missing spell slots, being able to find gold, and maybe like a capstone ability that replicates the effects of the Midas touch on an enemy, dealing damage and trapping them in gold briefly, only turning them into gold fully if the attack kills them. How would you guys go about implementing this and balancing this?

Implementing a money based warlock would be pretty damn potent if they are capable of just trading gold for spells directly. Do you see it as a support or combat focused subclass, seeing as you say it should be capable of finding gold.

The Midas touch thing is an actual spell, it’s called Flesh to Stone and it’s not particularly good. Either way, your gonna have to pick either balance or flavour.

Oh I don't need any of these specifically, just thought these would be fun Ideas. But yeah, I guess more support/utility could be a cool focus. Honestly, kinda like elements of the college of Mercantile bard subclass mixed with warlock, with a bit more of a focus on spending money for more magical power i guess? I think maybe a better capstone ability might involve being able to revive for a hefty fee of gold.