Hi Lauren, I have a place in Big Bear I have now been renting for 2.5 years I also manage cabins for people and consult on what places to buy - I'm the one who actually helped Michael Perez find an amazing home- and will be managing it for him.
Big Bear is GREAT 4 season for rentals as long as you buy the right place and you are very active in managing it. I'm not sure why anyone would say winters aren't good in Big Bear- I have been 100% booked on my place from Thanksgiving to Presidents Day every year so far. And this year will avg 225 nights rented on my home. Not everyone will do as well- but if you are available 24/7 to answer rental inquiries you should do well with Big Bear.
You do not want a condo and you HAVE to have a spa. You DO NOT want anything other than Big Bear Lake. 2, 3 or 4 bedroom will attract different people but won't really effect how much money you make per season. There are big families looking for 8 beds and romantic couples looking for 1 or 2 beds. I find my 3+1 makes as much as my 4+3. In the off season my 3+1 is booked most nights while my 4+3 is booked solid and I can charge a lot more during holidays.
There definitely are certain things you need in Big Bear to go from 100 nights rented to 200 nights rented a year. If you are looking for a consultant/management let me know, would love to discuss more.