To my mind both of these would be prohibited transactions but I wanted to make sure I wasn't missing anything.Thank you

@Jacklyn P.No, your IRA can not lend money to you or the company you own, that would be considered prohibited transaction.

The Checkbook IRA owned by an LLC seems to give you the most freedom and certainly the more exposure to the IRS if you perform a "Prohibited Action". 

But, in top of mind, the FHA prohibits discrimination on the basis of seven protected classes: race color religion national origin sex disability, and familial statusHope this helps!

For regulatory reasons, they are specifically prohibited from providing exactly the kind of legal and tax advice you need to self-administer a Solo 401(k) plan.  

@Michael A PiersonThe first thing is always to learn about how to use a SDIRA, the rules and regulations, and prohibited transactions.

I did not join their Elite mentorship program due to the prohibiting cost and some reservation comments on BP.

No minimum lot size requirementSetback requirements will be brought down to four feet (new construction only)No impact fees for ADUs under 750 square feet (graduating scale over 750 square feet) No owner-occupancy requirement for 5 years (will be revisited then)HOA are no longer allowed to prohibit ADUsAn ADU and a JADU are allowed to be built on the same propertyNo parking requirement if your property is located within half a mile from public transitSB 13 Parking Just Got EasierLet’s start with the heaviest bill.

@Rupert GrantGenerally if you're eligible for a Solo 401k, it makes sense compared to a self-directed IRA for many reasons: 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.You can borrow up to $50k from the plan; IRAs do not allow participant loansThere 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 :)The one exception I can think of is if your primary goal is to self-directed Roth IRA funds.

However, I am not sure that if this space is converted, it would be considered an Accessory Dwelling Units (ADU), which the city prohibits.