Tough one.
Here's a suggestion i have tried when my AS wanted me to buy something for him. I made him earn it. No handouts. He had to do work for me like yard work, cleaning the garage, detailing the car, small home repairs, things like that. I helped him and he helped me. If he didnt finish the work or do it well then he didnt get paid for it. Many times he changed his mind after he found out he had to earn it. Whatever you do dont give the money upfront - just like any job you work first and then get paid.