This is a great article and I highly recommend reading it. I learned something new too. Here is the link for tax rules for 2nd homes http://www.kiplinger.com/features/archives/2007/01/secondhome.html.
Here is the link for when you make your vacation home a business http://www.kiplinger.com/magazine/archives/when-you-make-your-vacation-home-a-business.html
The most important items that stuck out to me were the 14 day rule with personal use, making sure you factor in the lost investment earnings from your down payment, and the adjusted gross income exceeding $150,000. This is why it is very important to consult your CPA and Financial Planner too.
http://www.kiplinger.com/magazine/archives/vacation-homes-deal-or-no-deal.html
Now it does depend where you are buying but this article makes a great point as to why it is a good time. “Because real-estate prices have fallen much faster than rents, the math of buying a rental has actually improved substantially in most parts of the country. Money invested in an apartment complex today typically generates annual returns of 7% to 8% right off the bat, up from less than 6% at the peak of the housing bubble in 2006.”
“If your property appreciates in value or rents rise, you could end up with double-digit annualized returns when you sell it. But higher returns usually come with higher risks. If you overpay for a rental property or you buy in the wrong market at the wrong time, you can lose a lot of money.”
http://online.wsj.com/article/SB20001424052748703798904575069341576405172.html#mod=todays_us_section_b