I've been a solo dev for nearly a decade (8 years) and I found that sometimes it makes complete sense to pay for an office. Before my daughter was born, I was able to work from almost anywhere: noisy cafes, at home, the library, etc. But after she was born it was like my brain needed a space away from home where I could close a door and have a room all to myself, a place where I couldn't hear family sounds or be within walking distance of anyone I knew. I tried cafes and libraries but, oddly, they no longer worked for me—the noise and the people walking by suddenly became a huge distraction. I couldn't focus. I decided to rent a tiny artist studio for $350/mo that I found on CraigsList and it was the best $350 that I spent each month in terms of direct impact on my ability to get work done.