There's often unpleasantness when too-low rents have lulled tenants into a distorted sense ofa) the marketb) implied cost of regular maintenancec) healthy living conditionsd) the imperative of growing income, managing spending

From the other experienced landlords out there, is there any specific advice you can give me to help me avoid putting myself in an unpleasant situation?

They will tear your houses up, cause a ton of stress, and be generally unpleasant.

Do you have an unwanted or vacant property that you need to lease or sell?

You do not want to be unpleasantly surprised at move-out when your tenant has left holes in the walls or has completely destroyed your carpet and kitchen cabinets.  

Try buying and selling unwanted rural vacant land west of the Mississippi.We double and tipple our money on cash sales or throw off a 50% annual return for more than 10 years.

typically the lower the price the more unwanted location and run down properties.

Being ambitious or motivated tends to be emotionally driven behaviors and thus are bound to fade and falter once faced with any adversity or unpleasantness.

So, I figure I can sell the first two to pick things up in a market with appreciating rental rates but the transaction costs and the taxes of sale, together with the cost of closing on a new place seem unpleasant.

No misunderstandings... work through all the unpleasant what ifs that could come up... and do that before you even enter into a partnership.