Any mistakes along the way?

You also have to understand your end goal, they you just put the best debt you can at the time and plan for the worst. 

My suggestion - better in time and effort, and money (through the mistakes you going to make), than paying a guru.Between BP and books and all the other podcasts and blogs available for free, you shouldn't need any paid training - don't fall for that.

Negotiating against yourself is a huge mistake.

Are there any mistakes you wish you would have avoided?

Hardmoney is expensive. if you make any mistakes or under estimate costs or timeframes the interest alone could wipe out all of your profit very easily.

We made multiple mistakes in purchasing this building.

I have had the worst time getting the municipalities to cooperate. 

Don't leave that sort of thing up to the tenant, a mistake is too costly.

My buyer is in need of mitigating his medical collections payment, and I remembered hearing on a BP Podcast that “just paying it off” once it hits collections is the worst thing you can do.