Entrepreneur code of conduct?

I have a question for the community about my responsibility towards others. I have a side project that is close to being profitable (the iDAQ by tactitionprogramming.com), and I want to keep it a side project. I have gotten some help through the hacker community, and I try to give back where I can. Recently I had someone contact me who is developing a similar product, for a different market. The initial contact was under the guise of being a customer, but we ended up talking about the WiFi chips we are both using and I was happy to give some tips. After dropping off for a few months, I got another request for some assistance, and now his webpage has hints that he is edging closer to my target market. My response was a (slightly rude) offer of some example hardware and software for $12k. This got a response along the lines of: "Well.. how about I give you $50/hr for consulting?" Still mildly interested, I accepted, and then got stood up at our first Skype meeting. Oh, and 2 days layer he says he says he would still like to work together in the future. Assuming you enjoy helping where you can, when do you recommend telling someone you are not interested any more? Would most people even consider helping out with another (potentially competing) small business? I am looking for both a little feedback on my current situation, and also for advice in the future.