Here is another perspective on the topic based on some polling we did at local airports a few years back. Its a hot topic for new pilots looking to buy an aircraft, as many "think" they need a four seater before they do the math. Wives/Family are often touted as the justification.
You have to be VERY honest with yourself before committing to the financial demands of a four seater - especially if you intend to BUILD.
We polled pilots one year and 100% of the pilots stated they flew ALONE approx. 60% of the time, and with a SINLGE passenger 30% of the time. The remaining 10% of flight time had a total of 3 souls on board. Of those three on board group, most used the extra space for baggage/fuel as few could actually support a fourth person. Those flying with four on board regularly, and that is the key, REGULARLY, were too low to count as a %.
Good hopes and intensions aside, the reality is, guys with four seaters more often then not only fill the second seat on most flights. So you really have to make sure you have a true NEED for a four seater before investing the amount required. This goes DOULBE if you are considering building one. Its a lot of money unless you actually FLY loaded a lot -- Not just twice a year.
Remember, for those occasions when you actually NEED four seats, either for baggage or people or pets, you can still RENT, or BORROW, or PARTNER in one for a LOT less than owning or building. Especially an RV-10. I've known a few to go over well $210K without trying. Its a lot of $$ if you only fill it twice a year.
Like the others said, mission, mission, mission.
If you are a sport pilot for instance (acro, burger runs, ACM, formation, buzzing the neighbors cattle), you will not be all that thrilled with the limitations of the four seaters. So weigh zooming and booming against driving a bus from point A to point B. RVs are amazing SPORT planes. Making them into mini-airliners has its downside. Weight.
So if you have a wife and no kids, tell her to buck-up and stop trying to pack 200 pounds of **** for a two day weekend.
My wife loves the RV-8 because she has more shoulder room than in a side-by-side. She also prefers the all around view. My buddy and his girl love his RV-7 because he can share the work load with her and give her a kiss in flight. The RV-6, 7, 8 and 9 can handle enough baggage for a long weekend or extended trip if you have access to a washer/dryer at the hotel. So its not like you need a four seater for the occasional excursion if you are thinking in terms of BAGGAGE.
Family you say? When my son wants to fly, we rent or borrow a four place spam can. Getting the wife, kid and Dog together to fly regularly NEVER happens as much as one hopes or wants. One other thought, when the kid grows up, you are again back to generally only needing two seats and even before he moves out, a lot of flights will not include the kids because you and the wife are getting away from them for a much needed break (thank god for grandparents!).
Anyway, good luck which ever way you go. But don't be afraid the Rent a four holer when you need it and be a guilt free wannabee fighter pilot the other 60% of the time.