Your LLC and your flipping business are disqualified to your IRA. What you seek to do is not possible in an IRA as it would create a prohibited transaction.
A Rollover as Business Startup (ROBS plan) would allow you to use your retirement funds to capitalize a true real estate development company that you are engaged in, and that company could buy a truck. I would not, however, recommend that plan just for a truck purchase. If you have the available capital to fund the business to the tune of being able to execute 3+ flip transactions per year, then it might make sense.
If you are just seeking a work truck for the occasional flip project, just go out and find something used and inexpensive and pay for it personally.
Yes Cody, what you describe would be considered "prohibited transaction" transaction by the IRS. You and your immediate family members are considered to be disqualified party to your IRA, and as such are prohibited from entering into any transaction with your IRA.
You may want to consider Solo 401k which comes with the feature called "participant loan" allowing you to take a loan from your 401k up to $50,000. The loan can be used for any purpose, including investing in your own business. Each plan participant can get a separate loan so potentially you could access up to $100K of your retirement funds tax and penalties free.
Should you decide to utilize the ROBS 401k to finance a real estate operating company, the following requirements from the real estate operating company side of things will apply. This is in addition to the rest of the ROBS 401k requirements.
Real Estate Operating Company
1) The corporation that you invest your retirement funds in may invest in real estate that satisfies the following requirements:
a. At least 50 percent of the assets of the business, valued at cost, must be invested in real estate which is managed or developed and with respect to which such entity has the right to substantially participate directly in the management or development activities.
b. Such entity in the ordinary course of its business must be engaged directly in real estate management or development activities.
2) Expenses related to the real estate will be paid by the corporation.
3) The real estate will not be used for personal use.
4) There may be periods of time when the 50% test described in 1(a) above is not satisfied. This confirms that it would be acceptable as long as the 50% test is satisfied on the following dates: (i) the “initial valuation date” or the first date on which the corporation makes an investment that is not a short-term investment of funds pending long-term commitment; and (ii) at least one day during each annual valuation period. An “annual valuation period” is an annually recurring period of not more than 90 days that begins no later than the anniversary of an entity’s initial valuation date. For example, if the corporation’s first long-term investment is made on October 3, 2017, that date is its initial valuation date. The first annual valuation period can commence as late as October 3, 2018. An annual valuation period that commences on October 3, 2018 would end on December 31, 2018 and recur each October 3 through December 31 thereafter. Once an annual valuation period is established it may not be changed except for good cause.