You listed the advantages. what are the disadvantages? do you have storage somewhere else? does the garage currently house tools, bikes, holiday stuff or laundry?

do you have kids who will want the place down the line? an aging mother?

i am all for adding income potential to a property, but I dont know your situation.

I don't see the garage and your first step is to find out if it is allowed in your town to convert . Garages are not usually built to be living spaces so often the amount of work to change it is not worth it. They almost always look like converted garages too I fo one would not want to walk through a carport to get to my apartment .BTW you cannot include that in oyur home space since it is not part of the original home . The plumbing alone will be a big expense so if allowed then go looking for a contractor and get some pricing.

My first inclination is yes but if you are planning on renting I would investigate whether or not the is a pool of potential renters.

all great comments - I want to weigh the pros and cons. It is currently a "carport space" not a garage. I do have other space otherwise. Housing is in demand, and will continue to be that way for a time. I do have family that I may be able to have live with me in this space. It is legal to convert and rent in my area.

Do you want the headache of becoming a landlord? The stress of someone you don't know possibly tearing up your newly done apartment? Having to ask for the rent every month? The taxes involved in rental income? The responsibility of maintaining the place for tenants? I've never understood the mindset of so-called "slum" lords who just buy rentals for the rent money and do not renovate and maintain the housing. If you don't want to maintain it, don't do it.

When I was in college my parents converted an "over the workshop/garage" space into a studio apartment for me to live in my senior year (it was my idea!). We did all the work ourselves. Twenty years later it's still going strong and has been a great place for visiting family and friends to have some private space to stay while visiting over the years. Even during the pandemic they had a place to house visiting family while social distancing. They would never want to rent it out, but it's been great to have.

How popular are 250 sq ft apartments outside of major cities?

If the homeowner is in San Jose or nearby, this is probably a no-brainer, but you certainly need to check local ordinances/building codes before starting construction unless you intend to try to fly under the radar. A conversion of garage/carport space that is not up to code in my area (major NE metro area) would negatively impact future selling price of the property due to disclosure requirements when selling.

What you ar eplanning is an addition not a coversion at all. A carpot is not made for just adding a top and sides it has to be built to code and that is an addition or an ADU if allowed where you are .