Birds can be an exception; a medium to large bird can cause a lot of mess if not cleaned up after regularly. Many more landlords accept cats into rentals than dogs, since cats can be happy living in small quarters and are often cleaner. Small dogs are more likely to be accepted than big dogs for the same reasons.
Monthly rent for senior property for rental dwellings in the U.S. has increased in the first quarter of 2010, but in a slower pace compared with the last quarter of 2009. Meanwhile, occupancy rate in senior housing has declined during the same quarter.
After watching your so called 'stable investments' take a nose dive in the last year, maybe you've decided to take the plunge and diversify your investments. It's still a buyer's market and interest rates are the lowest they've been in years, so real estate is the logical choice.