I always viewed the run-up area as a place that I could get out of the way, take care of anything that I needed to, and prepare both my plane and myself for takeoff. When I'm ready, I'll taxi to the hold short line. Feel free to "pass" me while I'm in the run-up area, provided that you are...
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I'd recommend establishing a "Fair rental rate" that covers fixed/variable costs and associated reserves. Now your LLC has income. However, you want to minimize your income for tax reporting...
I'll probably do the same thing (sign up in the spring). Last time I looked at their website they were offering a couple glider flights for less than $200.
Where do you live? Perhaps one of us can recommend a flight school they've used, for private pilot lessons, advanced ratings, or continuing education/refreshers on specific topics. Also, what are your long term goals? Are you looking to fly for the airlines, or taking your family/friends for...
Another airport just down the road from King of Prussia is Chester County (MQS) http://www.chestercountyaviation.com/school_airplanes.cfm They have a Cessna 152, 162, several 172s, Piper Archer, Arrow, and Seminole. Runway 11/29 is a 5,400 X 100 :)