To answer the ops question, any possible upgrade is in inventory available to all owners... everyone sees everything thats available.
so if you see a possible upgrade for your friend by all means let the VIP you are renting from know its there so he can grab it for you
You could also grab it yourself, so it wont be lost and then later coordinate a cancel (from your account) and upgrade from the VIPs account
If I was the VIP you were renting from, however, I would have priced the smaller unit at market price and if you wanted a larger unit I would charge for that unit at market price as well. ie Ill get you that upgrade but you are going to have to pay
For example I have had a studio, a one bedroom and a two bedroom for the same holiday weekend. to rent and Im paying the same thing for all three of them...and thats half the studio price. and I charge market prices for all three. I will rent the two bedroom for more than the one bedroom and the one bedroom for more than the studio in spite of the fact that my cost was the same for all three.
Of course the VIP you are working with may not be profit motivated and may be willing to pass all the discounts through to you, and give you the larger unit for the same price as the smaller one.. Not me (unless you are a regular customer bringing me lots of reservations or a friend, or someone I owe favors to).
Bottom line the discounts I get are generally enough to provide me with the profit Im looking for and still offer the reservation at a good price to my customers.. I dont pass all the discount through to my customers I pass through only enough to make the deal.
what I pay for a reservation has very little to do with what I charge