As Mario states in his comment, there is a lot of risk of no payment, with lots of work. I wouldn't take this gamble.
What I would do though is show off your abilities, and offer your portfolio to the potential clients. It's easy to make a portfolio in a few days or a couple weeks, essentially screen shots of what you can create for them. Once it's made, you update it when you have new designs or new techniques available; otherwise, it's what you show to every potential client.
For web sites, I'd recommend 5-10 different designs, and get them screen shotted. Then, print them out on high-quality, high-gloss paper that looks amazing - you will spend money on this. Even better, posterboard! But, be aware it may get awkward to carry around. Then, go in with this, and your laptop. Have your portfolio on your computer (or the Internet, if you know there will be free Wifi), and let the customer look at what you have available. Give them the 60-second sell; most bosses/managers make their decisions rather quickly, so show your best works early in the meeting.
If they say no, it's perfectly acceptable to ask why, but do not probe repeatedly if they don't tell you why. After that, thank them for their valuable time, and politely ask if you can come around again in 3 months, 6 months, or a year, to get an update on how their business is doing. If they say yes, then you can start talking more about what you can do for them, and how inexpensive it would be, compared to the monetary returns they would be getting. What I mean is, if you are going to charge $1,500 for a website, you need to show how the customer is going to make $10,000 back.