But I can tell you, in retrospect, the only item we didn't address that I wish we had was replacing the hot water heater. 

Plead with the county's appraiser to retrospectively reduce the back taxes because they've been ridiculously overcharged for such a long period of time. 5.

In retrospect, especially when I was younger, I probably could have put some time into real estate.  

In retrospect, I feel that although the books I am about to talk about were extremely helpful in their own respects, they initially left me with more questions than answers because I picked them in the wrong order.

We never made a dime on CF, but in retrospect it did not matter, by holding the properties long term through thick and thin, we did way better than we otherwise would have.

In retrospect I probably should have made some moves or leveraged myself during the last crash, but I wasn't at a good point to feel comfortable doing so at the time.  

But in retrospect I would not do it again.A wise man once told me - figure out what your goals are and then put yourself on as direct a track as you can find as quickly as possible.

@Justin O'MalleyI didn't read every single post  prior to writing this but having taken a 401(k) loan I can say:- When I took it out, I said to myself "I will stick it out at this job for 5 more years to pay this thing back"- I took a decrease in take home pay to pay it back (obviously)- In retrospect I am glad I took out the loan as it lead to a good cash flowing property- I do not believe that the money out of my 401k would have been earning the same return that it is earning in my rental based on current market conditions- I am young enough (as are you) to make a fumble now and recover before I retire- (Not related to 401k) I am remotely familiar with the Denver market and believe that it is hyper inflated and would advise you to proceed with caution in that market especially if it means tying up your existing assets

Additionally my work with investors in Oregon and California has quadrupled and most of my recent clients have in retrospect secured very favorable terms on both the purchase and sale side. 

Retrospection for anyone like me finding this later on: BiggerPockets did this video a couple of years ago about what steps to go through when underwriting a property(such as what I'm looking at) and I felt it to be really helpful for getting an initial understanding of what "Underwriting" meant.