my dad passed away a few months ago. I have been collecting rent on 2 legal units and 1 illegal unit in a 3 family home. The rent is paid in cash there are no leases. My dad and i resided in the first floor apartment....

You might find a buyer at that price, but any financing appraisal will probably catch the discrepancy and may blow the deal. 

I found some discrepancies in the appraisal report, one being that they seemed to have not listed my 800 sqft detached garage as an amenity, the other being that they listed the closest comp as a two bathroom house when it is really just a one bathroom.I really need the appraisal to be about 30K more in order for me to be able to pull out some equity for the down payment on my next house.I don’t want to wait another year for another appraisal.

However:-The buyer's lender may require a survey-There will be an exception to coverage in the title policy covering any land discrepancy 

Why the discrepancy?

If you find discrepancies, you may want to call the property manager and explain the situation and ask him/her to provide statements/information surrounding the discrepancies and that you will get a lawyer if not.

Write all interested parties, mortgages, and liens listed in the complaint.Verify the owner(s) of the property Go to the county appraiser, tax collector and official records site (clerk of courts) make sure they all list the same owner If a discrepancy is found more research is neededSearch for filled Mortgages.Gather the chain of title from the property the appraiser and official records and do a name search for each person that held the title of the property and find the mortgages associated with those names.Search for Satisfaction of mortgages/release of mortgages, and assignment of mortgagesUsing the names for each mortgage found, search in public records for the satisfaction of mortgages for each mortgage found.Any mortgage left without satisfaction is an “active lien” , in Florida the oldest recorded mortgage holds the superior position (Unless there is a subordination of mortgage recorded)*MORTGAGE POSITION IS KEY….YOU WANT TO ACQUIRE A FIRST POSITION MORTGAGE!!!!....

For example, they would compare every lease to the rent roll and notate discrepancies, walk every unit and notate age of appliances, carpet condition, any evidence of water intrusions etc.- As @Charles Carillo mentioned, you want to partner with someone who is going to keep you informed. 

I would also suggest you start to go to all the open houses you can possibly manage in your neighborhood (or other specific neighborhood) even if you cannot remotely afford anything there...a big part of finding good deals is learning to evaluate properties relative to the market in which they are located (try to be focused on a narrow geographical area in the beginning)...visiting a lot of places will start train you to notice potential added value of places...the various discrepancies between the ad and the actual place...all skills which are transferable to whichever market you will decide to focus on later.Feel free to DM if you have any questions 

@Tina McDonaldThere's a large discrepancy in answers you'll get to this.