Yep, that's the default. The guest pays the same share as anybody on the team, assuming that they draw on the same resources.
If the guest has his own paint sposor, for example, it is unlikely that he would be able to offer paint to the entire team, but if he is supplying himself with paint, he shouldn't be expected to pay for a share of team paint.
If The team, however, is sponsored with paint, for example, it would be reasonable to expect that that sponsorship would include guest players who do not choose to supply their own paint.
Guests should be informed if they are not able to use sponsored gear that is not used by the team before both parties agree to play together. For example, if the team is a JT team, and the player ordinarily plays for an Empire sponsored team, JT may prohibit guests from wearing competitiors' product. This should be brought up as early as possible, so that the guest can find out policies/ obtain permission from any sponsors that they have who would be in conflict with the teams' sponsor requirements.
If the guest has a sponsor for some part of kit that the other party does not, he should be allowed to rock that gear by the team. If the team has sponsorship over some part of kit that the guest has no sponsor coverage for, it is at the descretion of the team and their sponsors whether to supply the sponsored gear, whether as a loaner, a permanent gift, or at some discounted price for mandatory purchase. It is pretty cheeky to require a guest to pay full retail for some equipment that a team is sponsored by.
These suggestions are what I consider to be reasonable defaults. Any exceptions to such rules of thumb should be discussed, and in fact these ideas should probably be confirmed or denied before anyone agrees to anything. Courtesy on the part of both parties should be the guide.