We tried various formulas over the years as membership could not agree. We have a variety of ownership types on the road, including year round, seasonal, land only, on lake frontage, no lake frontage. We tried charging based on year-round versus seasonal but some places were built for year round use and owners would come during the winter. We lost in small claims court trying to enforce it. Then for years we only asked for donations. About 4 or 5 years ago when the laws changed (greatly improved, I'd say) we finally agreed and voted that our dues (fees) would be based on the City's total valuation on the property. Our mill rate has been the same each year but we vote annually to set it. We have it at .002 (or .2%) of the City's total valuation. The law says it cannot be more than 1% of the City's valuation and with this method we are sure not to exceed it. Once the formula was set up in Excel it has been fairly easy to do a mail merge with Word to send out assessment bills. I can access the City's real estate data base on line so after my tax bill from the City comes, I know I can go on line to get current valuations and owners' names and addresses. We have about 70 different properties with about 50 different owners. This method is working quite well and we have only 3-4 who have not paid. These are mostly owners with annual bills of $5 to $10 who are out of state and land only, no lake frontage. Another road nearby has a set annual fee of about $150 but that road has no year round owners. It is more homogenous. Good luck.

We, too have a wide variety of properties. We took the approach that although people choose to use their properties differently (seasonally vs year-round, etc.), we all have equal access, so, with the exception of the 1% cap, we tax all properties equally. We are considering limiting the roads we maintain and offering discounts to those properties that do not abut maintained roads. 

If you review all the topics, I think you will find past answers to a similar question.