How do people go about finding practice space? A friend of mine added a small ballroom to his home, putting in the necessary items for it to be an efficiency for an elderly parent to live there, so as to pass codes, but the bulk of it is one open floor--but I don't have the money to add on a ballroom.

My place has NO large spaces. The livingroom, if I got rid of ALL furniture, might be big enough to practice in a bit, but the rest of the family objects to the idea of having no place to sit.

Where do people go to find space to dance?

If you take lessons at a studio, there are often times when the floor is available for practising. At my studio, I pay $7.00/hour for practice time. Friends rent an empty classroom at a nearby school once a week to practice. Go to studio parties, you can practice your steps while working on floor craft. Getting around the floor and not bumping into anyone is a large part of dancing.

Studio parties? What are those?

I do not live in a large city so what is available is very limited.

I think the idea of renting a classroom is a good one, I'll see if that sort of thing is done here.

$7 an hour is not too much for practice time, IF there is a studio that will do it. Most around here turn the air off and there is no point in paying anything for space if it is 110 degrees with 90 percent humidity inside. I'll check on that too though, in case I could get lucky and find a place that will rent the time with the air conditioning turned on long enough to cool it off.

Practice space is a tough one.
Studio parties are generally held at dance studios, sometimes as part of the lesson package they sell. You get a certain number of lessons, plus a "social party" at the studio, which, as LadyDance mentions, often turns into a practice session because most of your classmates are there as well as the instructor. But you can go to these as a guest any time, so it wouldn't necessarily have to be your studio, etc. You just show up and pay anywhere between $5 and $10 for two or three hours of time, with a good assortment of music, usually all at strict ballroom tempo.
I don't teach at a studio, but I do teach at the homes of people interested in learning, or at my home, which has a decent amount of space and all of the music I need. I don't have a great surface however, as it is a thin carpeting. But it works, and you can do several sequences of a dance without running out of room. But when I am at the student's home, we make due any way we can. Some setups are better than others, but we do as much as we can to be able to "travel" around a room as needed. Some obstacles are fine, for when you are teaching hesitation turns and such.
Another option is to find out if there is a community center or church in your area that allows use of rooms or basement space, etc. Sometimes you can approach a church or a community center and make a pitch to start a "club" of some sort of people who want to practice ballroom and exchange ideas and techniques. It's worth a try, considering your situation. In exchange for use of the room, you can offer to pay for its use or ask if they need volunteers for anything in the future as a trade-off.
Less likely, but still possible, would be to look for open retail space -- empty storefronts or business lofts. Contact the owner and ask if you can use the space on occasion in exchange for cleaning the place up or painting something, etc.
For one group of people I teach, we use the hair salon where one of the ladies works. We use it on the night it is closed, and it works fine. If you can stumble across something like that, or have a friend in the hair/spa business, they might be able to help, too.

Thank you for the suggestions. I'm going to see what the cost is at the place where the instructor here uses.

I need to check around, I recall hearing about a dance club here that meets monthly and they have a buffet dinner and dancing. Not cheap, but it might be a fun activity.

I found a solution. At the gym where we workout there are handball courts with wood floors. I asked and found out that in the middle of the day they are usually not occupied and we can check one out and dance!

Have space! And then we can swim to cool down.