How much money can I add to Stable Balance?

How much money you can add to Stable Balance depends on two factors: 

The first one is the Wallet Service you're using, as each federation wallet has its own unique limits as defined in its metadata by the guardians. These Stable Balance limits will soon be visible in the Fedi app in the Wallet Service Details section of the relevant federation.

The second one is the available liquidity provided by the stability provider, which is used to lock in the fiat value of your Bitcoin for a fee. If this liquidity is low, you may not be able to lock all the desired balance you want to add to Stable Balance even if you haven't reached the Wallet Service limit.