There are professionals who have spent years picking up a lot of little things through formal training and learning by experience. 

I understand that I can present comps that have sold in the area to a formal assessor review but does anyone have any other strategies they have used in the past to decrease the assessed value of a single family rental?

You should charge him a late fee if you have it in an agreement, but it sounds like you don't have anything formal.

@Epi Villarreal  private money loan .. or a loan from a formal HML company.Most private folks don't charge a fee for an app.. most lenders only charge for apprasial and credit report.. those that charge on top of those are generally just looking for easy peasy revenue.. you send 550 in and they may or may not do loan but they are ahead 550

The degree can be in anything, the major is not the point, it's the level of formal education they want in the profession.

Although we have a formal mentoring program here, wherein a mentor is assigned and you both agree to a service/compensation arrangement,  I never used it.  

Others disagree, but you can read those debates here and decide for yourself.Pretty much the only difference you'll have from a tax perspective is that in an LLC you may have an additional deductible expense for maintaining the LLC with the Secretary of State, an additional expense to file a tax return and more formalized bookkeeping and corporate governance duties.PS - I am right up the road from you in Arvada.  

I am formally promoting you to CEO of this local movement and look forward to the date and time I need to arrive. :-) 

I have no back round or formal education in investing and I am learning as I go.

In 2008 I sold my commercial property formally known as Buffalo Radiator (63est Utica..