So I would venture that all of your examples could very easily be demonstrated to be held with the intent of productive use whether or not they generate revenue quickly or consistently throughout the year.But the RV is another story - It's not real estate so it doesn't qualify for 1031 treatment (although I do love that idea if you'll forgive me. 

So I've been looking through different websites searching for multi-family properties and practicing to analyzing them using the BP rental calculator and every calculation I've done is nothing close to a deal.

If no one comes to the door, look the property up on the county tax website and send them a letter.Good luck!

For instance, in the morning when I wake up I would check the RE websites such as realtor.com or zillow.com.

You can also verify them on the FL Security of State website.

Property tax websites are unreliable, as they are typically only updated around the time tax bills are sent out, which is only once a year in my county.

What are some ways of generating income in addition to renting out the residence in a house like this?

The websites @Anthony Angotti mentioned are great for find properties that have sold. 

@Dawn Anastasi has a contractor list on her website and I would trust her recommendations.

How much cash flow will it generate and can the property afford to give up 10%, do you have time to manage it yourself, and probably the biggest in my opinion are you wanting to get into this game long term or is this just a 1 time 1 property deal?