You can roll over the gain from one piece of investment real estate to another to another and another.

Jeff, The issue I am facing with is due to the amount of time it will take to roll the funds from my existing ex-employer's 401k plan to a new solo-401k plan which I was hoping to use to fund this property.To give you an example, let's say this property is contracted for 300K.Let's say I have one IRA account with TDAmeritrade say with 100K, Schwab with 100K and a 401K plan with JP Morgan with 500K.Previously I had inquired with TDAmeritrade, Schwab, and JP Morgan and they all told me all it takes to roll over to another IRA provider is 3-5 days. 

She was actually kinda pissed I didn't roll over and I wound up financing the difference, but got my price.

The mechanics of it is we roll over 401k funds from a work 401k and start a personally-directed 401k.

@Jason RyersonThe Self-Directed IRA and Solo 401k Differences CONTINUEDThe solo 401k business owner can serve as trustee of the solo 401k;The self-directed IRA participant/owner may not serve as trustee or custodian of her IRA; instead, a trust company or bank institution is required;When distributions commence from the solo 401k a mandatory 20% of federal taxes must be withheld from each distribution and submitted electronically to the IRS by the 15th of the month following the date of each distribution;Rollovers and/or transfers from IRAs or qualified plans (e.g., former employer 401k) to a solo 401k are not reported on Form 5498, but rather on Form 5500-EZ, but only if the air market value of the solo 401k exceeds $250K as of the end of the plan year (generally 12/31);When funds are rolled over or transferred from an IRA or 401k to a self-directed IRA, the amount deposited into the self-directed IRA is reported on Form 5498 by the receiving self-directed IRA custodian by May of the year following the rollover/transfer.Rollovers (provided the 60 day rollover window is satisfied) from an IRA to a Solo 401k or self-directed IRA are reported on lines 15a and 15b of Form 1040;Pre-tax IRA contributions on reported on line 32 of Form 1040;Pre-tax solo 401k contributions are reported on line 28 of Form 1040;Roth solo 401k funds are subject to RMDs;A Roth 401k may be transferred to a Roth IRA (Note that from a planning perspective, it may be advantageous to transfer Roth Solo 401k funds to a Roth IRA before turning age 70 ½ in order to escape the Roth RMD requirement applicable to Roth 401k contributions including Roth Solo 401k contributions and earnings.)

They do not typically hold any cash other than for brief periods when you may be moving funds into or out of the structure at the IRA layer like with a contribution, distribution, or plan-to-plan rollover. 

time sure has flown by thus far. it's amazing how everyday its something new. one day she needs held up, the next she does it all on her own....one day she can't roll over, the next you find her in her crib sleeping on her stomach. it's craziness!

You can roll-over from a regular IRA to a SD-IRA.  

Have a rollover-IRA from prior 10+ years of employment parked at Vanguard.

If you roll over and give up, they are.