If you would want to use IPN you will need to set up a script that paypal will call once payment has been processed or failed. This is useful if you don't want to have to check everyday for the payment.
But for you application, if you don't need it to be automated a simple buy button could work.
Here is a pauy button with some inputs not hidden...
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<label>First Name: </label><input type="text" name="first_name" value="" />
<label>Last Name: </label><input type="text" name="last_name" value="" />
<label>Email: </label><input type="text" name="payer_email" value="" />
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="email@youraddress.com">
<input type="hidden" name="lc" value="US">
<input type="hidden" name="item_name" value="youritemname">
<label>Account Number: </label><input type="text" name="item_number" value="">
<label>Dollar Amount: </label>$<input type="text" name="amount" value="">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="button_subtype" value="services">
<input type="hidden" name="bn" value="PP-BuyNowBF:btn_paynowCC_LG.gif:NonHostedGuest">
<input type="image" src="https://www.paypal.com/en_US/i/btn/btn_paynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>
Hopefully this is somewhat what you want.