@KaJay
Thanks for the clarification. So it sounds like the tax professional has determined this individual is an an employee and not a self employed individual. Again, for 415 purposes the plan limit is 100% of plan compensation. If there was no other income other than the housing allowance, this is a 415 violation of 100% of compensation. IRC Section 402(g) limits the amount of retirement plan elective deferrals you may exclude from taxable income in your taxable year, which is generally the calendar year. Your 402(g) limit for 2024 is $23,000 (2023 is $22,500; 2022 is $20,500; etc.). If the only compensation for plan purposes is zero, then there is no compensation to defer any money into roth or pre tax
Since they are allowing up to an additional $10,000 in EMPLOYER contributions, the employer contribution can stay, but the entire deferral and earnings are disallowed. This remains roth as you cannot change roth contributions to pre-tax contributions after the fact. It's been a while since I encountered this, but I think the $10,000 amount you are referring to is a lifetime limit, not a per plan year limit.