It may depend on what you want to do with the software. What is your intent?
If you are interested primarily in using it to record information, then there are many software tools that basically function like an accounting package. Gita Faust has a quality Quickbooks solution / training / program.
If you're looking for transaction support -- e.g. Advertising, Running Credit Checks, Collecting rents electronically (automatic and recurring), or Managing maintenance problems -- then you'll want a different kind of solution.
Here are some best-of-class recommendations for each transaction type:
[list]Advertising - RentMarketer.com
Credit Checks - Tenant Network
Collecting Rents - PayRents or RentPayment.com
Finding Maintenance Personnel with user reviews - Angie's List, CircleChoice.com
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If you're looking for one place that does all of those things in one place, then my company is one that can help. Our value proposition is twofold: first, it saves a lot of time and hassle by going to a single place to solve all these problems -- single sign in, simple pricing; second, by negotiating in bulk, we're able to get and pass on to customers a much lower price.
It really depends on what's important to you and how you want to spend your time and money.
Jeff