I have a client who would like to establish a defined benefit plan to provide their maid (63 years old, retiring in five years) with an annual benefit between $15,000 and $20,000. I seem to remember seeing something that allows a householder to sponsor a plan for domestic help, but I haven't been able to find anything on point. Does anyone have any advice?

A plan for Domestics may be established, but there is no deduction permitted. That is because running a household is not a 'trade or business'.

What do you think of setting up the domestic as a business then contract with the business for domestic services and have the business have a solo k or whatever for its sole employee?

That was my thought originally, but I'm not sure the client trusts the employee to take the additional pay to fund the plan.