I can relate. I'm currently living in my husband's childhood home in his native Italy with him, our son, his mom, sisters, their spouses, and their children. There are 13 of us, and we each have apartments, but we eat every meal together, and my in-laws spend most of their time in the common area of the house.
This is my husband's reality. He has always lived with lots and lots of people. It's no big deal to him when we're in our home in the United States (in which just the three of us live) to have guests, who stay with us for months. It's not about money for us. In fact, it costs us more to have them stay with us because we don't charge them rent or have them pay for food or electricity/heat. They are our friends, who need a place to crash because they are usually visiting the United States from Italy.
We once had an Italian female friend of ours stay in our basement in the States for three months when we hadn't been married a year yet. (She ended up celebrating our first anniversary with us, in fact.)That situation, even more than living with my in-laws (which is family, so it's slightly different) taught me a lot about marriage.
One of the major lessons I learned is that married couples, especially newlyweds, should not live with other people if they can help it. Our friend was quite respectful and never showed interest in my husband. But she's an attractive, young woman, and she and my husband grew up in the same place, have the same friends from Italy, and went to school to learn English together. Sometimes, I'd get left out of the dinner conversation. And they are both natural flirts, which would get on my nerves. I would cook, clean, and keep up with my full-time job, and I felt like they were getting to have too much fun together. My husband was always in the main part of the house with me and she lived in the basement and they are both good people, who didn't show interest in a relationship with one another - sexual or otherwise - but it brought unnecessary tension to our marriage in its earliest days. I wondered, out loud on some occasions, if men and women can be just friends after marriage.
Of course, we overcame the jealousy and inconvenience. And we're still great friends with our former roommate. What I've learned from reading the forums is that having roommates actually suits some couples. They find it to be fun and they enjoy having company. Plus, it did help many of them save money. Still, the majority seem to think roommates are bad news. Of the 234 votes taken on the Weddingbee site, 198 were for "No way, we would ever take in a roommate." The discussion that follows this poll is an interesting one worth viewing if you are considering having roommates or already have them. It includes a range of opinions.
Since most couples seem dead set against having a roommate, read "Roommates - What to Consider" to find out what to consider when deciding whether there is room for a roomie in your marriage.