This is just my observation, but maintenance costs will be greater the first couple years before settling down. I budgeted for what I thought would be a steady state maintenance plan. I actually found with both airplanes ownerships that the first 2-4 years yields increased maintenance costs. Some cost is associated with the previous owner neglecting certain items, but the biggest reason is that a new mechanic's focus areas are different from the previous. This was even with a thorough pre-purchase inspection. That was really the only surprise in my budget.
Something I haven't seen mentioned is subscriptions for different items. GPS database, publications/EFB/foreflight subscriptions, Alaska Airmen's raffle, ice classic, BCP hat, PlanePerfect cleaners, etc. I understand that some of these won't pertain to your interests.
I use a separate account to manage all my aircraft expenditures so that I can audit my budget from time to time and make sure I've accounted for everything.
Brett
