You will then obviously have to add additional costs, such as title search fees, title premium (which will vary depending on the cost of the property), recording charges, plus any loan fees (and escrows) depending on whether you are financing the transaction or not.  

All I'm really saying is: don't pretend that the portion of ones 2-4plex property managing income comes under the category of "real estate professional" (afaik).

I've found that the Trulia heat map is pretty good in our markets, Indianapolis and Kansas City, but it's usefulness varies by market.

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I have looked up rental rates and found a good price point to offer the 2 rooms, especially since they are varying in size.

You’ll need to check local codes but if it’s zoned duplex, but currently the use is single family, you should technically be able to convert it if you bring it up to code (IRC - the version varies by jurisdiction) which requires attached two unit dwellings to be separated by 1 hour fire separation.

They are all listed in the mobile home category if they're in a mobile home park.That said, acquisition prices tend to be much less than a stick built home on owned land.  

Is this true for all counties or does it vary by county/ city like Baltimore / Annapolis or Montgomery / PG County , and come down to local jurisdiction?

If you plan on purchasing or flipping other properties chances are the best company, based on price and coverage will vary on the properties. 

Given that your rent income is $1675/mo, and using a 75% figure for what the bank will give you (this varies), I get $1256.25.