And his plan is transfer his money from his foreign company into his U.S subsidiary.

Membership Withdrawal & Transfer Provisions6.

The bank may or may not make an issue of you transferring it into an LLC.

Also, watch out when taking a property 'subject-to' because many states consider this a transfer taxable event, so as the property goes into your name, or the name of a trust you decide to use, you may be liable for transfer tax - not a huge deal, but something to be aware of.

@Victoria DransoffYes the IRA and the real estate holding can be transferred to a solo 401k plan.

For payment of the loan amounts, do I need to have him make out two separate checks/transfers each month or can one check be deposited into the Traditional account and then immediately transfer the appropriate amount to the Roth account (based on % of initial loan amount)? 

If it's an excise tax every time title transfers, then you'll have what WA does (1.7%) and Philly does (4%). 

I am interested in transferring my 401(k) from my previous company into a Self-Directed 401(k) - NOT a Self-Directed IRA - for the purpose of investing in cash flowing rental properties.

For example, I have seen some properties in Indiana where taxes doubled within the last year and there was no transfer of ownership.

The money is transferred to another escrow account where it is transferred to the lender to make the payment on the loan.