Hi Charles,
You're taking the right course by checking with your 401(k) provider to begin. I don't believe you would be allowed to invest in real estate or to transfer funds out to an IRA prior to separation of employment. It's generally after termination of employment that people rollover their 401(k) from a former employer.
That said, on the off-chance you're able to do so, it actually [/i]is permissible to "partner" your IRA funds with personal funds to make the investment. The key is that the only time you're able to do this is at the time the home is purchased. That is[i] allowable. But if you tried to invest personal funds into a home your IRA owned already, or tried to invest IRA funds into a home you owned personally, that would be a prohibited transaction as described by Mr. Beard. To read more on prohibited transactions, see Internal Revenue Code section 4975.
Another thing you would need to keep in mind is that, in order to partner your personal and IRA funds to make the investment (only permissible at the time the home is purchased), technically you would need to be able to demonstrate the means to purchase the home personally, without using your IRA. (Being able to purchase it personally would include purchasing it with a down payment and bank loan; it would not have to be all-cash). As Mr. Beard mentioned, the "self-benefit" rule restricts you from personally benefiting from your IRA; were you unable to make the purchase without using the IRA, then its usage would mean you were benefiting from it.
I hope this helps. You might give the folks at The Entrust Group a call. They can talk this through with you.
Gary