Should I sell a project I'm not passionate about to pursue new projects or take advantage of the position I'm in and stick with it?

Hi, I'm in a bit of a unique position. I built a lead generation website in a very boring local service niche that does very well and beats out 95% of the competition in Google for the biggest metro area in the US (New York). I charge per qualified phone call to the client who pays weekly. My position is this: I do not want to operate as a lead generator (middle man) any more as I feel this is not a stable business model for the future. So that being said I've decided I want to become owner or part-owner or sell it off and move on. Based on loose math I've done it could be a nice payout based on 1 years's worth of revenue it brings into the client if I were to sell it. Though, I'm wondering if you were in the position of getting hundreds of phone call leads per month for an industry you had zero passion for if you would stick with it and build it into a bigger/higher quality operation or sell it off to the client and move on to new projects that may be more in line with your passions and personal interests. I know this is a very subjective question and there probably isn't a 'right' answer. I feel that if I were to sell it I might wonder if I missed out on a stable business for the future (if I were to build it out) and if I didn't sell it I would be working in an industry that I don't care about and does not fulfill me. Thanks!