Here are some recommendations for you:Find and connect with other BP members that are in your area: http://www.biggerpockets.com/meetSet up keyword alerts to be notified of the topics that interest you: http://www.biggerpockets.com/alertsRead Beginner’s Guide: http://www.biggerpockets.com/real-estate-investingCheck out BP Podcasts: http://www.biggerpockets.com/renewsblog/category/podcast/Wishing you the best!

Brandon Turner put a book out on this topic I think it was called the Complete guide to rentals or something like that and I think it describes his screening process. 

After some research, it seems, there is nothing illegal about it, as long as there is not active knocking/engaging with the home owner, as well as staying away from communities whos HOA has a no trespassing signI get them all the time at my house, but they are usually for restaurants, which isn't offensive at all, which is why people probably won't complain and much as "I would like to help you sell your house if your house, etc"If anyone has any advice or knowledge about possible fines associated with this it would be much appreciated. 

Most state regulations require a landlord to evict a hold over tenant if they do not leave voluntarily.You should not have agreed to allow them to stay beyond the end of their lease.

Please click on the links, give them a read, and share your thoughts in the comments.First is a post that I feel will help not get overwhelmed with the amount of info that is here on BP:https://www.biggerpockets.com/blogs/5868/52761-the-simple-guide-to-getting-started-on-bpThe second is a post that will help get you focused with your real estate investing goals:https://www.biggerpockets.com/blogs/5868/52743-im-new-to-bp-any-advice-would-be-appriciatedThe last one is a post that will help you choose an “investor friendly” real estate agent.

If she doesn't leave, begin eviction for a holdover where, in many jurisdictions is much easier to win a judgement than for non-payment or other lease violations (where they can just show up to court with the cash and they get to stay, despite your time and court costs).Also, it would be very helpful to us for you to put your RE market in your profile or at least in your post, because in this part of real estate, too, location matters. 

Her husband and father came to help her move and stayed a couple days.

I don't know why choose to stay in something that makes 8% so they can save taxes today that they are going to pay taxes on in the future (when they are in a higher bracket).

I didn't know much about real estate at the time but I wanted to learn from him because he seemed to know a lot about it, so I thought he could guide me through the process by having me invest in a place and showing me how it is done.

Stay firm on your requirements.