Reading the buy-laws, there does not appear any legal reason for us to refuse it.However, for my peace of mind, I was curious to know if there could be any risks associated with an investor buying more and more units to the point where they could force the demolition or vote decisions detrimental to the residence. 

I'm currently with Realty Executives Associates, where I help manage a portfolio of rentals.  

This realtor is using the standard lease agreement from the association of realtors and told my sister she doesn't need to sign it.

I currently am 19 years old, live in PA and in the last semester of getting my Associates degree in Business Administration.

In addition, you have the issues of HOA fees, special assessments, fines because of tenants breaking rules and regs of association, and rental restrictions imposed by the HOA.

I currently work as an analyst at Kingsley Associates, a real estate market research and consulting company.

Look to your local Home-Builders association or Home Inspection Association for good contacts. 

It will report things like, this applicants past address is associated with multiple incidents of fraud etc.  

I am in a good cash position but of course would like to stay that way and not weather any hits from the condo association.

The listing agent still technically represents you anyway, and as liabilities associated with you, fess on the buyer side, etc.