Incentive fund is an enrollment used to generate more interest in showing. Basically once you enroll and keep it going it generates money for the breeder if the person continues to show the horse. It to me is a plus in any horse.
The APHA has the Breeders Trust as their enrollment which is similar.
Hopefully some who are more knowledgable than I can help me with the rest.
When you show a horse and earn AQHA points not only does the breeder of that horse receive money at the end of the AQHA year but so would you. I am not for sure what the going rate is now, but you have to show and earn points at an AQHA show. If you are going to show AQHA anyway it is worth it to find an incentive fund horse.