Most trust management systems will provide a potential purchaser of a rent roll with a management statistics report.
Generally this will show the statistical information of the portfolio or the rent roll, such an average rent, gross fees, letting fees, number of properties managed, number of landlord, arrears etc. It is important for a potential purchaser however, to obtain the actual commission rate charged for each property managed to review whether there is a variation in the rent commission charged across the rent roll.
The value of the rent roll is in part based on the commission charged. That said there should be a price variation or lesser multiplier paid on a rent roll where there are a number of fees charged at 4 or 5%. It is too hard to increase the commission rate to 6-8% as owners will resist this increase. Therefore as a conclusion, the higher the commission charged, the higher the multiplier a buyer will pay.
If you own a rent roll, start the process to increase your commission rate over time and to do this in conjunction with increasing your rent. It will be hard for the landlord to resist pay a higher commission if at the same time they are getting a rent increase.