Buying new obviously correlates to less repairs/maintenance. Buying a brand new property shouldn't need anything doing in the first few years. If it does, chances are the builder will take care if it for free.
The downside to buying a new property is it will most likely cost more than an older one. However the amount of rent you will receive after all the costs (NOI) will be higher. Your decision here will be your own personal preference. I would recommend buying almost new properties (less than 10 years old). With the current economic climate, it is possible to buy almost new, bank owned properties at a very large discount but this will be personal preference. For example if you are a tradesperson then there should be a substantial saving.
