I only flip houses to buy more rentals. I only invest in p2p because I need to show reserves for loans. p2p is far better than money sitting in a bank account. I won't touch a rental unless I can get 20% cash on cash return. If I were to calculate in principle pay down, my returns would be much higher. My all in costs are always under 80% of full market value, so I have built in equity as well.
Owning or flipping properties is a business and is hardly passive. That could almost be said about the guys who clock watch attempting to get p2p loans. I don't think it matter how you define them. The biggest question should be, is the time commitment, risk and profit allowing you to reach your goals. P2P serves its purpose, as does real estate investing, as does my job.
Jason