1) SaaS w/ monthly subscription
2) I'm about 8 months in and monthly revenue has finally ramped up to a point where, if I were to make this much each month, profits would be well over $50k
3) The biggest hurdle has been customer acquisition. The first chunk of customers I got through a deal when starting the company. The rest have been a struggle. Managing marketing efforts while still hacking all day is a lot of work. I also have no real internet marketing experience. One other hurdle has been dealing with a deadbeat co-founder.
4) I started with one co-founder but he has since gotten a job and I have quit mine. I'm working 100% full time on the startup and he hasn't contributed more than an hour in the past 4 or 5 months, so it's pretty much just me.