Good handymen are far a few in between. Usually anyone that has good general knowledge of construction moves up the ladder to doing their own GC work.

What were the tasks?

Not sure if you are asking me the question, but for me it was to put together a cabinet (I ended up doing that myself in less than an hour) new weather stripping and add peep hole on front door. Last 2 still on my list.

$500 for that? I'm in the wrong business.

Never pay in advance for materials unless you personally know him and trust him.

Pay when materials are onsite.

Have seen this go either way only a few times and what I've learned vicariously is ... 90% of the Owners would choose a different course.
a) hire a contractor that has good enough credit to buy whatever, then 1/2 through (1/3 for plumbers) ask for a progress payment or reimbursement using receipts
b) open your own line of credit for your workers to charge to; best if you get a call before the products leave the supplier for your approval

You don't want to go & buy the wrong stuff yourself and also not get any in-the-biz discounts offered.