I have invested in this are a few years ago, and I have worked with a few of the builder that built serveral of the new homes back in and around 2003, and investors as well I may be able to answer some of your questions.
I have an investor purchase closing this week. It is the Fannie Mae Homepath program at 90% LTV. This is my customer's first investment property, so we had to count the full amount of the proposed payment against him. He was able to qualify for both that payment and the payment on his principal residence.
The maximum no. of financed properties that most lenders are allowing is 4, including the primary residence, just so you are aware of that rule. I am not aware of any guidelines that allow up to 10 financed properties as in the past.
As to your other question, about equity in the present home, there is no requirement for equity in the present home if the borrower is simply purchasing a rental property. There may be cash reserve requirements as determined by each particular lender's guidelines.
Hope that helps...
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