Prebuy
Yes, yes I do recommend a prebuy on every aircraft one is considering.
While searching for an airworthy RV-7 to buy last year I completed FIVE prebuy looks. The fifth uncovered several things that had to be addressed, but they were manageable and the price of the plane reflected its actual condition.
I bought the plane and fixed a long overdue AD that hadn't been complied with, cleaned and updated some items, sent in the mags for a 500 hour inspection and documented everything clearly.
At my first annual condition inspection an A&P and I were not surprised by anything unusual or too exciting.
Please don't take any offense, if you are a builder selling your plane. The fact is that a builder who has his repairman's certificate for that plane may have missed something. If no one else ever looks at the plane it gets missed every year during the annual condition inspection. Also, as builders lose interest and decide they need to sell their baby it can get neglected for the next few years until they get up the nerve to actually put it on the market.
Vic Syracuse has said and published a great amount of information on this subject. Here's a few things I found to be true from conducting prebuy's on RVs as well as certified aircraft with an A&P helping me:
1. Save a lot of time, money and frustration for you as the potential buyer and the seller by asking for a complete digital copy of the log books, yes all of them, the airframe, engine and propeller. Go through them carefully or have your A&P that will be doing the condition inspections in the future go through them. It is worth paying for this service.
a. Verify all data is present to determine the date of manufacture for the engine, serial numbers for magnetos, prop hubs, blades, etc so an Airworthiness Directive and Service Instruction search can be performed.
b. Knowledge is key to making an educated offer. Base your assessment of the aircraft's value on true condition of the aircraft. If it needs a 500 hour magneto inspection or AD performed, consider the cost to have this completed.
c. Look for documentation of maintenance on things that are required to be done. If the seller says the mags were inspected at 500 hours, or a prop reseal, there should be a record of it, even if he did it himself. Better if critical maintenance items were performed by a reputable shop with receipts and official logbook entries to match.
d. Every applicable Vans Service Bulletin should be addressed in the logs. Recurring inspections called for by service bulletins recommending yearly checks for known issues should be recorded at every condition inspection. Asking for specifics and for pictures of those areas highlighted by Vans Service bulletins is due diligence.
2. If the logs check out digitally its time to ask for some more detailed pictures. Chances are this sweet looking RV is half way across the country and depending on the responsiveness of the seller and his preparedness to sell his plane, a digital "preliminary prebuy" can be done in a morning if all things are squared away. Many sellers already have detailed pictures of every angle taken at the last condition inspection when they had all the panels off and everything was clean because they were already thinking that they might sell their baby someday soon.
3. If the seller is unresponsive or sends pictures that are clearly from 10 years ago (it happens) then a decision will need to be made whether to pursue the purchase or not. Ask the seller if they would be willing to fly their plane at your expense to an A&P of your choice an hour away for a prebuy look. Their response will give you a sense of how confident they are that it would pass a prebuy without a lot of costly fixes.
4. Conditional offer. Before the seller actually flies the plane to the A&P of your choice it may be wise to secure the first right of refusal by making an official offer. AOPA has formated conditional agreements that I've modified for my use. A conditional offer can't prevent the seller from allowing someone else to swoop in and buy the plane out from under you, but it helps communicate your intent to buy as long as everything is as portrayed. Confirmation of condition by an A&P during a prebuy look is how you can be sure the aircraft is what was advertised.
5. I like to look at things I'm buying in person, even if I bring it to an expert to evaluate. This is where I might bring a down payment in cash to make an official purchase agreement with the seller, look at the aircraft and logs in person and make a final determination.
I suppose I'm cheap and want to avoid over paying for things, so I look closely before buying. Some people don't mind buying a pretty plane and then having a mechanic spend a few weeks going through it to fix and upgrade things. In the end, we are all going to pay before we buy or after, it is just a matter of time.