I currently have 5 mortgages but have not been great at keeping track of the details such as costs associated with each individual property.

This is because keeping a property nice has associated costs.  

Our goal is to sell the first plat with the house and use the money to build a modest modular duplex on the other plat to rent.We are both very inexperienced when it comes to building and renting, and need all of the information we can get- what are some unforeseen costs associated with building a modular?

Yes, provide as much information to the tenant as possible with a detailed list of all the excess expenses that are associated with the tenants damage to the property.

Although, there are costs associated with forming and maintaining an LLC, such as state filing fees and annual reports that are to be noted. 

Best advice I have is join Apartment Owners Association of California, aoausa.comThey have a lot of resources for landlords. 

The problem with super high cap rates is newer investors don't realize the headache factor/risks associated and think they simply print money. 

However, I would advise staying away from anything located a hundred miles south of Birmingham due to the risks associated with the Gulf area, including parts of Louisiana, southern Mississippi, and southern Alabama.

The most important thing to remember when interviewing Brokerages is that you are interviewing them, so many new agents treat it like a standard job interview and think they are interviewing for a job not a Brokerage to associate with.

It removes the forced timeline associated with 1031 while providing the same tax delay benefits.