If he was going through a divorce, his ex could have accused him of something to get custody of the kids. 

@Emily RefiThe two common choices for investing retirement funds into real estate are the self-directed IRA and the Solo 401k.The Solo 401k requires self-employment activity, but will allow you to take participant loans while the IRA does not.A few other Solo 401k benefits: Compared to an IRA, Solo 401k contributions limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.The penalties for prohibited transactions are less severe, though it's best not to utilize this benefit :)With either structure, it's generally recommended that you do not commingle retirement and non-retirement assets.

I had planned to open both custodial accounts and Roth IRA for them, then pay them through online payment from our business account to their custodial accounts, then transfer the money into their Roth IRA accounts.

You'll also have custodial fees with them. 

Here are some factors to help you make an informed decision:SDIRA vs. e-QRP:SDIRA (Self-Directed Individual Retirement Account):Allows for a broader range of investment options, including real estate.Provides more control over investment decisions.Requires custodial services, and there may be fees associated with the SDIRA provider.Strict rules and regulations to ensure compliance with IRS guidelines.e-QRP (Enhanced Qualified Retirement Plan):Similar to a 401(k) but with enhanced features for greater flexibility.Generally, more streamlined than SDIRA with fewer administrative requirements.Allows for real estate investments, business investments, and more.May offer more control and fewer restrictions compared to SDIRA.Financing Considerations:Both SDIRA and e-QRP can be used for financing, but the terms and conditions may differ.Check with your chosen custodian or plan administrator to understand the borrowing rules and any potential penalties.Tax Implications:Understand the tax implications of using retirement funds for real estate investments.Consult with a tax professional to ensure compliance and to minimize any adverse tax consequences.Market Conditions:Consider the current real estate market conditions in the location where you plan to buy the beach house.Evaluate potential risks and rewards, especially in the context of your investment horizon.Long-Term Strategy:Since you're planning to work for another five years and potentially sell the house later, ensure that your investment aligns with your long-term financial goals.Interest Rates and Economic Conditions:Monitor interest rates and economic conditions, as they can impact the timing and profitability of your real estate investment.Professional Advice:Consult with financial advisors, tax professionals, and legal experts to get personalized advice based on your specific financial situation and goals.Due Diligence:Perform thorough due diligence on the property, renovation costs, potential rental income, and local market trends.Remember that real estate investments, especially with retirement funds, require careful planning and adherence to regulations.

Here are some of the reasons why: Compared to an IRA, Solo 401k contribution limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.The penalties for prohibited transactions are less severe, though it's best not to utilize this benefit :)

When they are being picky, it is just to protect the integrity of their paper trail for the regular custodial compliance audits they undergo. 

I'm a single Dad with sole custody of both of my kids.

Applicant: A one bedroom, but I'll need a 2 bedroom once I go to court to get back custody of my kids. 

Some people like the custodial style and some people like the speed and ease of checkbook control.