[JohnFen]

This might depend on where you are. In my area, it's unusual to have to provide a retainer at all unless you're doing something big or the lawyer suspects you might have trouble paying your bill later.

[phasetransition]

In my personal experience with small firms closed ended matters like wills, contracts, or individual IP filings don't require a retainer.

Open ended matters, like probate, starting an IP portfolio, or response to a C&D trigger a retainer.