Look for code related to "Accessory Dwelling Units." Some examples of the standards in our area are... it has to be less than 720 square feet and the property owner is required to reside in the primary dwelling or the ADU.

Please keep in mind your responsibility to your future tenants and their health and safety as you plan this project. It's probably not going to be cheap if done properly.

Considering low cost, how much do i conservatively need to build 1000 sqft for the rental property?

You probably won't be allowed to build a 1000 sq ft residence on your property.

Accessory Dwelling Units are great, if they are allowed in your area. The thing is, making an actual, rental "home" involves kitchens,s plumbing, and electrical, among other things, so there's kind of a minimum cost involved regardless of size.

Research "tiny homes" though -- some really cool things out there, although whether you would be able to legally rent it is another story.

Not on this planet.

you could build a yurt --

1000 sf code compliant with everything you need? 200k to start with. And another 200k for the lawyers and fines.

$150,000 minimum. likely more. could be lots more

Thank you guys. Since it's a rental property I don't need to make it fancy or complicated. I may need to buy some floor plan online without architect. Then I may need a crew to build it. Simple and low-cost are the goal. Is $100k do-able ?

A yurt sounds like a good idea to me. Surely that would get a small home the cheapest way?

Permits alone could be tens of thousands.

I don't know CA, but I think you're dreaming. Last year I found the average cost to remodel an existing house was $100-150 here in Oregon. And with the market on fire, I've heard construction rates have following suit and skyrocketed.

I couldn't help myself and quickly looked up Accessory Units in Santa Clara. If all the lot requirements are met, one is limited to 640 sq ft, with a full kitchen, one bed, one bath. Santa Clara City Code - Accessory Unit

Are you in city or unincorporated county?

I assume you are intending to build with permits. California has various structural, fire safety and other requirements for a reason. If so $100k is not going to do it. You might be better off exploring prefab units.

I think accessory units are a great option. Adding one is the next phase of our home renovation.

I think it might be time for you to do some work. Here's a basic 25x25 one bedroom floor plan. (Just an apartment layout that popped up on a Google search.) Tweak it to your available space, talk to the permit office, talk to some GCs, etc.

"Since it's a rental property I don't need to make it fancy or complicated."

No, but it has to be LEGAL and COMPLY with building codes ... that means permits and good construction practices.

First find out what is LEGAL in your city ... you might not be able to legally do any sort of garage conversion. If you do an illegal conversion, you will probably have to not only pay to do the conversion but pay to remove the conversion.

Look for reviews of the rental property and the landlord or management company. This will give you an idea of what to expect from the property and the people you will be dealing with.

Remember to do your research thoroughly, read the tenancy agreement carefully before signing and be wary of any red flags that might indicate fraud. With these tips, you can find a great rental property online.