Recently, I discovered that I'll likely have to repair the foundation of my house to prevent any new cracks from forming through the cinderblock walls, however, I'm not sure other large expenses I should look out for.

Quote from @Eric Stewart: There are ways to prevent this, or at least dramatically reduce the likelihood of it happening again.1.

I know a lot of the major players in the Realtor department in my area.

Trust is the biggest name of the game.Also knowing who is responsible for what before you get started is a great way to prevent an argument. 

I would suggest a darker shade of granite to prevent any stains.

I would NOT recommend this company to my worst enemy and I hope that I can prevent others from being scammed by WealthAbility by posting my personal experience on as many forums, websites, platforms as possible and by filing complaints to every agency out there that deals with consumer fraud.

It could prevent a host of problems this summer.

I suppose the things you mention could happen, but many of the 'things you put in the contract' are put there because one bad thing happened a couple years back and the attorney recommends it to prevent that bad thing from losing you money.

I could rehab them with a line of credit then sell them above the release price to prevent paying at closing. 

So I strongly recommend that your rental have its own bank account.As for worries about the mortgage bouncing - the only way to prevent that is to fund the rental property's account up-front with some reserve capital.