Nope. Let's say that it does need a full-time programmer. You pau $200,000 for this site assuming it will pay for itself in 4 years. But, since it requires a full-time programmer, you have to quit your job. Now you're just in debt. So, for the first 4 years, you have no income as you pay off $50,000 of that $200,000 each year. Well, that won't work. In fact, the government is going to want some of that in taxes, so it will probably be 6 years where your income is $0.

I don't think it's a stretch to say that a decade is a long time for a site to stay relevant and in a good position. As such, if 80% of the money from the site goes to paying off the site, it isn't worth much. If it requires you to work on the site full-time, it's worth nothing since you'd be loosing the income you could get at another job.

Whether you're doing the work or someone else is doing the work, if you have to quit your job, then the site must be able to satisfy your income PLUS profits that make the investment worthwhile. You've said that the income is a reward. So, would you pay me $200,000 and work for me full-time for 10 years for me to give you $50,000 per year for those 10 years? No! You could get a job paying $50,000 without paying someone $200,000. Now, let's say that you only had to work 3-4 hours a week. That's a VERY different story.

Do you see where I'm going there? A site like the one described is a good investment if it can be a little site project that doesn't take much time. If it requires you to work full-time on it, $50,000 will cut it IF you don't have to buy it in the first place. If you have to pay $200,000, you might as well just get a traditional job paying $50,000 and not have to pay the $200,000.