@Jeff Caravalhoare you sure you have a custodial Solo 401k account?

@Patti Robertson, you are correct that he does not need to take a withdrawal in order to but at the auction, however, he is going to have a hard time doing so using custodial account.

Most, if not all, banks are not going to provide this because their IRA accounts are part of their custodial account system.

A qualified intermediary must be involved prior to the sale to take custody of the proceeds, document the 1031 on the sale and purchase closing settlement statements, and help you wade through the other requirements such as timing, title, and valuation.From the way you discuss it I get the sense that you understand the issue of intent to hold vs intent of resale.  

Between the two, the Solo 401k offers many additional benefits if you're eligible: 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.Welcome to Bigger Pockets!

You can do so directly in the custodial account.

We currently live In Tampa florida and I'm waiting on custody court for my son that I have with another female to go over based on us moving there.

We currently live In Tampa florida and I'm waiting on custody court for my son that I have with another female to go over based on us moving there.

It will also provide quite a few benefits over an IRA: 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 :)

He has joint custody of 2 children from previous marriage and I believe he gets to claim one of them on his taxes.