I have thankfully reached a point in my career where I am self-sustained. I don't spend a dime of family money for anything book related. But it took me a little while and several books to reach this point. My incredible husband never complained once. Whenever I was worried about the cost of books or an event, he would always tell me he knew I would earn it back. And you know what? I did.
You also need a supportive husband who will allow you not only time to write, but time to sell. My husband helps a couple hours a week with the kids so I can have some non-late writing time. He also takes the kids for two weekends a year (including using his vacation time at work) so I can attend writing retreats. I make time for my husband so we can cultivate and continue to build our relationship. We have a date night once a week and a couple nights a week I write for a little less time so I can still spend quality time with him. But he also doesn't give me a guilt trip when I say I need to write tonight. He understands how important my career is and I can't have that career without adequate time to write.
It's important for your husband to have his own hobbies too. My husband loves to play video games. I'm not a gamer at all. So the nights I work, he plays, and neither of us feel guilty because we both get to do things we love and also make time to do things together.
Whenever I have a book signing, it's usually an all-day event. It's even oftentimes a two day event. Again, my husband has to use his precious vacation time at work to take Friday off. He has to play mom and dad to our three awesome kids, which is super exhausting! But he does it with a smile, he kisses me as I walk out the door, and he never questions me. Whether I sell one book or fifty books, he always makes me feel successful. And you can't get any better than that.