First, many thanks to user 'glwright' who helped me figure this out.
Here is working code with only the site domain obfuscated. Note that PayPal has a 'sandbox' mode for testing plus the live site to accept real payments. There are two 'return' links. One returns to my 'Thank You' page which triggers an email to be sent. If the customer clicks cancel while at the PayPal site they return to the &cancel_return URL where you can tell tell them their transaction was not completed.
On the PayPal site you must do the following:
1) Set up a payment button, but you do not need the code from there. All you need is the generated button ID to include in the code below
2) In your PayPal Profile/Web Site Payments Preferences: set Auto Return ON
And in your form's Begin Submit piece include the following code:
// ---- Paypal Processing ---------------------------------------------
$business = "OnlinePayments@mydomain.org" ; // email addr for your PayPal merchant acct
$rurlraw = "http://mydomain.org/index.php?option=com_facileforms" .
"&ff_name=arcRNEW12&ff_page=1&Itemid=142" ; // raw URL for return
$rurl = urlencode($rurlraw) ; // url encoded
$canurl = "http://mydomain.org/index.php?option=com_facileforms" .
"&ff_name=arcRNEW13&ff_page=1&Itemid=143" ; // raw URL for cancel
$cancelurl = urlencode($canurl) ; // url encoded
$PPURL = 'https://www.paypal.com/cgi-bin/webscr?' ;
$button = '1234567' ; // PayPal Button ID
// Adjust if Test Site
if ($site == "Test") {
$business = "ken_1234567890_biz@mydomain.org" ;
$rurlraw = "http://mydomain.org/test/index.php?option=com_facileforms" .
"&ff_name=arcRNEW12&ff_page=1&Itemid=142" ; // raw URL for return
$rurl = urlencode($rurlraw) ; // url encoded
$canurl = "http://mydomain.org/test/index.php?option=com_facileforms" .
"&ff_name=arcRNEW13&ff_page=1&Itemid=143" ; // raw URL for cancel
$cancelurl = urlencode($canurl) ; // url encoded
$button = '9876543' ; // PayPal Button ID
$PPURL = 'https://www.sandbox.paypal.com/cgi-bin/webscr?' ;
} // site = "Test"
$item_name = "Club Membership Renewal" ;
$amount = $AMTPAID ;
$logo = "http://mydomain.org/images/site_logo.gif" ;
$retmsg = "RETURN TO Our Club to COMPLETE YOUR RENEWAL" ;
$data = "cmd=_xclick&business=$business&item_name=$item_name&item_number=1" .
"&amount=$amount&no_shipping=1&cancel_return=$cancelurl" .
"&no_note=1¤cy_code=USD&lc=US&cpp_header_image=$logo" .
"&address1=$ADDRESS&city=$CITY&state=$ST&zip=$ZIP" .
"&first_name=$FIRSTNAME&last_name=$LASTNAME" .
"&return=$rurl&cbt=$retmsg&custom=$Badge&rm=2" .
"&hosted_button_id=$button" ;
$url = $PPURL . $data ;
ff_redirect("$url","top","post") ;
// That's it ----- You do not return to here;
// but to one of the above return URLs
