No HAP contract until it passes, so I'm eating the vacancy either way

The sequence you described is the sequence. A tenant with a voucher finds the unit, submits a request for tenancy approval to the housing authority, the authority inspects and checks that the rent is reasonable, then the housing assistance payments contract gets executed and payments begin. Nobody can pay you for a unit that hasn't been approved.

What landlords do to shorten the window is mostly front-loading. Have the unit genuinely finished before the request goes in, because a fail resets you into the queue. Hand the tenant the paperwork you're responsible for the same day rather than a week later, since an incomplete packet sits. Ask the authority whether they'll accept the request while your make-ready is in its last few days, because some will schedule on a promised date and some won't, and that answer is specific to your authority.

On the first payment, ask two things in writing: whether payments run from the effective date of the contract or from the date of execution, and what their normal lag is between execution and the first deposit. Some authorities pay a prorated amount back to the effective date, and if that's how yours works, part of the vacancy you're worried about gets recovered. Some don't. It's worth knowing before you decide how you feel about the three to seven weeks.

And yes, the reliability afterward is a real part of the trade. It doesn't make the carrying cost disappear, it just means you spend it once per tenancy rather than every time a market tenant's paycheck wobbles.

The proration question @rena-guide raised is the whole thing and I'd never thought to ask it. If the effective date is the day the unit passed and payment is retroactive to that date, your seven weeks turns into maybe two of real loss. If it isn't, the seven weeks is seven weeks. Same program, two very different numbers, and you only find out by asking your specific authority.

I came into this looking for income without a second job, and threads like this keep telling me that the first month of every tenancy is the second job. Three to seven weeks of unpaid coordination per turn is not nothing. What I can't work out is whether that's front-loaded once and then genuinely quiet for years, or whether the annual recertification and reinspection bring a smaller version of it back every year.

@marlow a smaller version, yes, and how small depends on the authority. Annual reinspection is a scheduled visit you have to be available for or provide access to, and the recertification paperwork mostly lands on the tenant, though you'll get asked to confirm rent and utility responsibility. It's hours, not weeks.

@quarry, the compression trick that works in my portfolio is having the make-ready punch list built off the inspection checklist rather than off what looks finished. The failures I see are almost never cosmetic, they're the same eight or nine items over and over. If you want, the other thing to ask your authority is whether they publish their inspector's checklist, because some hand it out and it makes the whole timeline predictable.