Short answer: Unincorporated Castro Valley has no short-term-rental permit. You still need a county business license and must collect a 10% transient occupancy tax. In the City of Hayward, stays of 30 days or fewer aren’t legal. Your parcel, not your mailing address, decides which rules apply.
Own a rental in the Castro Valley or Hayward area? Short-term rental rules differ sharply here. That matters if you’re weighing a conversion for a turnover unit. The first question isn’t occupancy or nightly rate. It’s which government has jurisdiction over your address. In this corner of Alameda County, the answer isn’t always what your mailing address implies.
Same ZIP code, two completely different rulebooks
Castro Valley and the unincorporated county
Castro Valley, Ashland, Cherryland, San Lorenzo, and Fairview are unincorporated. Alameda County governs them directly, not a city council.
The county’s zoning code has no short-term-rental category. It sets no permit requirement, no cap on nights, and no primary-residence rule. So nothing resembles what Alameda city or San Francisco have built.
You do need a $20 county business license and a $4 CASp fee. Both renew every January 1. You must also register for, collect, and remit a 10% transient occupancy tax yourself. Airbnb doesn’t collect it on unincorporated listings, so you pay it monthly.
County home-occupation rules bar renting rooms to more than four people. An HOA’s CC&Rs can also override all of it, whatever the county allows.
Hayward’s 30-day rule
Meanwhile, Hayward sits half a mile away by road. It’s a different government, and its rule is the opposite of permissive.
The city’s planning guidance says every rental unit must rent for more than 30 days. That includes ADUs and junior ADUs. However, there’s no owner-occupied exception and no hosted-stay carveout.
Hayward doesn’t issue short-term rental permits, because nightly and weekly stays aren’t legal there. A 16% transient occupancy tax (as of February 1, 2026, under Measure NN) applies only to stays of 30 days or fewer. That tells you the tax exists mostly to catch violations, not to license a legitimate business.
Why your mailing address isn’t enough
Here’s the part worth sitting with. A Castro Valley or Hayward mailing address doesn’t tell you which rulebook applies to a specific property. Check the parcel against the county’s jurisdiction map before you assume either answer.
What the market data actually says — and what it doesn’t
Short-term revenue
First, treat this as a starting point, not a verdict. Rabbu’s market data puts Castro Valley short-term rentals at a $301 average nightly rate and 45% occupancy. That works out to roughly $25,988 in average annual revenue.
Hayward listings average $129 a night at 44% occupancy, or about $16,820 a year. But the city’s own 30-day minimum complicates those numbers. Any current nightly listings there sit in the unincorporated county despite a Hayward mailing address, or they operate outside what the city says is legal.
Because of that gap, check the parcel first. Don’t assume the market average applies to you.
The long-term lease comparison
Now compare that to a conventional lease. Rentometer puts average Castro Valley rent at roughly $2,583 a month for a 2-bedroom and $3,459 for a 3-bedroom. That’s $31,000 to $41,500 a year, before any vacancy or turnover costs.
The numbers aren’t directly comparable. The short-term figures blend every size and condition of listing in the market. They also don’t project earnings for a specific bedroom count.
The honest takeaway: don’t assume short-term is the higher-earning move. It depends on your property, your real comps, and your occupancy assumptions. That’s why we never hand an owner a market average and call it a projection.
One tailwind worth knowing about
Nationally, AirDNA’s September 2026 U.S. Review found RevPAR up 15.3% year over year. New listing supply growth fell to just 1.6%, the slowest pace since the pandemic. AirDNA ties that to 30-year mortgage rates, which climbed from 6.66% at the end of August to 7.28% by the start of October.
Fewer new listings and rising RevPAR is a real tailwind for owners already positioned. It’s not a reason to skip the parcel check. Instead, it’s a reason to run the math now, rather than assuming nothing has changed since last year.
What to actually check before you decide
First, confirm jurisdiction. Call the county if you’re not sure whether your address is in incorporated Hayward or the unincorporated Eden Area.
In the unincorporated county? Then get the business license and TOT registration in place before you list, not after.
In Hayward proper? A short-term conversion isn’t legally on the table, whatever the market data shows.
Either way, don’t let a blended market average stand in for real comps. Pull comps at your specific bedroom count and condition.
Have a Castro Valley or Hayward-area unit turning over? Our listing audit is free. You get a straight answer: jurisdiction confirmed, real comps pulled, and a conservative-to-upside range instead of a guess.
Frequently asked questions
Yes. Castro Valley is unincorporated Alameda County. The county’s zoning code has no short-term-rental category, no permit requirement, and no cap on nights. You need a $20 county business license and a $4 CASp fee. You must also collect and remit a 10% transient occupancy tax yourself. An HOA’s CC&Rs can still prohibit it.
No, not for stays of 30 days or fewer. Hayward’s planning guidance says every rental unit, including ADUs and junior ADUs, must rent for more than 30 days. There is no owner-occupied or hosted-stay exception. The city issues no short-term rental permits.
Your mailing address won’t tell you. Castro Valley, Ashland, Cherryland, San Lorenzo, and Fairview are unincorporated. However, Hayward is a separate city. Check your parcel against the county’s jurisdiction map, or call the county, before you assume either set of rules applies.
No. On unincorporated listings, you must register for, collect, and remit the 10% transient occupancy tax to the county yourself, monthly.
Not necessarily. Rabbu shows roughly $25,988 in average annual short-term revenue in Castro Valley. Rentometer’s average rents of $2,583 a month (2-bedroom) and $3,459 a month (3-bedroom) equal about $31,000 to $41,500 a year. The figures aren’t directly comparable. Pull real comps for your bedroom count and condition before you decide.
Sources
Rabbu, Castro Valley, CA Airbnb Market Data and Rabbu, Hayward, CA Airbnb Market Data (both as of April 27, 2026); BNBCalc, Alameda County, California Short-Term Rental Regulation Guide; BNBCalc, Hayward, California Short-Term Rental Regulation Guide; Rentometer, Average Rent in Castro Valley, CA (as of November 14, 2025); AirDNA, U.S. Review September 2026 (published October 8, 2026).