Totally agree with Howitzer. Sec 23's are often miss sold to people on the basis of the tax break.
Sec 23 relief applies on any profit you make. So when interest, management fees, maintenance fees are taken away, there should not be a lot of profit left. Therefore you are paying a lot of money for a tax shelter that will take you years (more than 10) to derive any meaningful benefit from. Sec23 were a god send for people that have lots of rental income and lots of taxes on their profits-in some cases they are able to save 5 figure sums in tax in the year of purchase of the sec 23.
My advice if you are new to this, is to avoid sec 23 and buy a standard property. They are better value, often better located(but not always) and definately easier to sell-generally! No certainties in anything!!