Based on my experience, there are many people that will ask to see only single-story homes and will not even consider two-story homes. There are much fewer people that will want the opposite - only two-story homes.
Having said that, two-story homes are typically bigger (more sqft) than single-story homes and they allow for a smaller home footprint -> bigger yard.
Single level homes are typically more expensive per sqft than two-story homes. I am selling a community in Avondale where the single story homes are around $90/sqft, while the two-story homes are below $70/sqft.
Now to answer your questions:
1. "Is two stories property harder to rent out?" - Everything else being equal, it is typically easier to rent a single-level home. More people looking for single levels exclusively than two-levels exclusively.
2. "How about the rental price" - because they are more sought after, single levels will typically rent for slightly more than two-levels. However, each neighborhood is different. Ask to see comps for single level and two level homes. They will give you a pretty good idea about rental prices.
3. "and property appreciation?" - that is an interesting question. I haven't seen any analysis on appreciation differences between single and two story homes. My gut tells me that they should be comparable. But I can't back it up with hard data. Sorry!
Bottom line: as long as you buy right, you can make money with both single level or two story homes.
Jose Dias, REALTOR
email: jose at MyFirstHouseAZ.com