Edit: With the money from behind the house it works fine, I think that the money that the girl in the cementery gives you is bugged and when you buy the dildo the game doesn't recognize it.
Is the balance accrued after receiving money through missions?
The fact is that only a personal balance is tied to the purchase of a Strapon. You need to have the required amount to purchase. And without performing third-party tasks you can buy.