Does a self-directed IRA fund a second note before the first one closes, or does sequencing the capital matter more than the yield gap

The sequencing question you are asking is the right one, and the yield gap is almost irrelevant next to it.

A self-directed IRA (SDIRA) is a retirement account you control, but your custodian still processes every transaction. That ten to fifteen business day funding window is real, and it runs from the day they receive a completed direction letter, not from the day your first note pays off. So even a clean April balloon repayment lands in your account, then waits for paperwork review, then funds the new loan. That chain very likely runs past the builder's February deadline without any extension.

On the smaller bridge loan idea: the math does not work with $6,200 in free cash. A 12k to 15k loan requires 12k to 15k in the account. You cannot split-fund a private loan from two sources inside an SDIRA, and you cannot personally contribute funds to close a gap once you are in the deal. That IRS rule matters here because you normally cannot inject outside capital into an SDIRA mid-year beyond the annual contribution limit (currently $7,000 for most people under 50). A bridge note would need capital you do not currently have available.

The cleanest path is probably an honest conversation with your Sahuarita builder about a realistic closing date. If the April balloon pays on schedule, you are looking at a May funding at the earliest. Some builders will take that.

One thing worth confirming with your custodian directly: whether they will accept a direction letter before the incoming funds settle, and how they handle note extensions if your April borrower asks for time. Custodians vary on both.

A tax professional should weigh in before you commit to the next note, since any structure that looks creative inside a retirement account can trigger prohibited transaction rules.

What does your custodian say their process looks like for back-to-back note funding specifically?

The line about your wife's instinct not applying inside a retirement account, that one I'd push back on. The instinct is exactly the same, the stakes are just higher because you cannot paper over a mistake with a wire from your personal account. That argues for more patience, not less.

Sahuarita is specific enough that the builder's timeline pressure matters in context. That submarket had some spec inventory drag going back into mid-2023, so a builder who needs a commitment by February on a 14-month note is telling you something about how his draw schedule is structured. You want to know whether April is actually his start date or whether he is already pulling permits and needs the money before your balloon clears, because that changes whether "later close" is a real option or whether he says yes while quietly finding someone else.

On the mechanics, I have seen SDIRA custodians at the slower end run 15 business days even on clean payoffs when the originating note servicer mails a check rather than wires, and that adds another three to five days before your custodian even starts their clock. April payoff does not mean April funds, it means late April or early May at best, and that is assuming your borrower does not ask for a 30-day extension. A genuine 60-to-90 day gap between commitment and available capital is realistic here.

What do your borrower's payoff mechanics look like, does he wire directly to the custodian or does it route through a servicer first?