Questions about first transaction (buying duplex)

[George Frick]

Hello,

 I'm a newer member from Milwaukee, WI. I've been mostly reading and not trying to barge in with specific questions. But I have some that I haven't found online or in the forums.

1. What happens to the security deposit when purchasing a duplex? Should we consider it lost, or will it be discounted from the purchase price? Is this something to include in our offer?

2. Are we allowed to for example; knock on the lower units door and ask them questions? Would we be violating something? I've been working through the training course for the Wisconsin realtor license and so far nothing says I can't?

3. Many duplexes are advertised with statements like "fully leased for the entire X years the property was owned!". This doesn't mention turnover though. If the duplex is a mile from a university this means nothing. How do I find out if the tenants are always moving in during the spring and out the next spring?

4. If I look up a property online, I can get the owner (and usually their phone #). I assume it is bad form to contact them directly?

5. If we put 25% down for the first property, this leaves us with almost no way to get a second property. Do most people here just save? A lot of people have a goal of one property a year. With this as an example; how do you build those funds?!? Do we take an equity loan on the existing properties for the down payment?

Thanks and sorry for the noob questions.