Can you do it alone? Is it possible?
Wrong questions (sorry, Amy Hoy for stealing your thunder.)
Should you even _want_ to do it alone is a much better question.
Building a SaaS alone is something I, a developer with 30+ years experience, would have serious doubts about. Yes, nowadays there are tools that make our lives as developers much easier. Ruby on Rails being just one of them.
The trouble is that there is so much more to running a SaaS, than “just” getting your 1.0 out the door. For example the little matter of running and maintaining that SaaS — dealing with inevitable bugs, support questions, and feature requests; getting 1.1, 1.2, 1.3 etc. out the door; figuring out what needs to go in 2.0 and building it. I’m sure Amy can give you a whole list of everything I am leaving out or aren’t even thinking of.
Unless you love building and maintaining software, building a SaaS alone, even with the very productive tools available today, will take you away from what you love doing, just like many entrepreneurs start a business in what they love doing and then end up managing the business instead.
Can you do it with a good partner, versed in software development?
That is already a much better proposition with regard to the actual software development, and it would enable you to focus more on what you love doing. However, it comes with its own set of challenges. Partnership is like marriage and finding the right partner like dating between species.
Don’t get me started on finding a good developer to partner with. Let’s just say that his or her grasp of technology will be a lot less significant than most people think.
You’re right in not wanting to offer equity. I wouldn’t go as far as Yegor Bugayenko in why you shouldn’t, but I do agree that offering equity should not be a substitute for paying for good work, unless you go full partners.
By the way, I don’t agree with many of Yegor’s ideas and don’t much like his extremely command & control (and divide and conquer) style of running software projects, but the people working for him are happy with it, it seems, and he does tout that he does not make his customers pay for “frills”.