If the owner REALLY needs the money, he might be willing to make a deal like this - but then you're investing in a business that is pretty desparate - does not bode well for the future of your investment.
You would need to get a return from this that exceeds significantly than what you can get in a passive investment to make this a good deal for you. This is to compensate you for your risk of investing in a small business vs say the S&P 500 which has returned nearly 10% annually over time. We need at least 12% here to make this a good deal for you (probably much more in reality) - so in your 200/month example you should not be willing to pay more than $20,000 for this.
Now, the business owner will make this deal if it is a good deal for him - how is it a good deal for him? If his cost of capital is currently greater than 12% - meaning to raise the funds that he needs, he has to pay more than that to someone else. So this guy cannot borrow at less than 12%, nor sell a piece of his business to someone else for less than an expected 12% return. Bottom line, if he takes this deal, he is desperate, and much larger companies than you as an individual are not willing to make a deal this good for him. This means he this business is likely a larger credit risk than you think, or is more likely to fail than you think.
So yeah as pucksr says, try to avoid bartering unless you've got information the other party doesn't and so can take advantage - odds are you don't have as much info as the business owner in this set up, so any deal you make is unlikely to be to your benefit.