So marriage is the only option if I want to have a woman live in my house while my child is with me (I have 50% child custody).My question is:  If I get married to a woman who works, how do I ask her to contribute to monthly expenses? 

Your contribution limits are higher, over three times as much can be contributed to a Solo 401K than a Roth IRA.Furthermore, Solo 401Ks are much handier for you, the investor as there are no third party custodians that can slow transactions down, and thus there are no custodial fees.

“Whenever any money is required to be deposited in an interest-bearing escrow savings account, in accordance with section 511.1, then the lessor shall be entitled to receive as administrative expenses, a sum equivalent to one per cent per annum upon the security money so deposited, which shall be in lieu of all other administrative and custodial expenses.

Custodians are permitted to custody assets held in an IRA under IRC Section 408.

I use Canada Western Trust and I believe Olympia Trust and Laurentian's B2B Bank and Eastern Trust offer custodial and servicing for arms-length mortgages in registered accounts.

The Solo 401k will offer many advantages over the SEP such as an employee deferral contribution (allowing you to contribute more money at various income levels), no custodial requirement, no need for the expense and administration of an LLC to receive checkbook control, a participant loan feature, and an exemption for unrelated debt financed income tax for many investments.Welcome to Bigger Pockets!

Compared to the self-directed IRA, Solo 401k contribution limits are roughly ten times higher and there is no custodial requirement for the 401k.

Equity Trust is common good customer service.You want to get a contact for a number of custodial firms.

Then under that, I have, "Conrad Rentals, LLC does not discriminate based on race, color, national origin, religion, sex, familial status (including children under the age of 18 living with parents or legal custodians, pregnant women, and people securing custody of children under the age of 18), and disability." 

Basically all of the investments through that, we have been guided on by the custodial company.