This mindset will save you a lot of unnecessary grief. 

In hindsight, the extensive foundation work was overkill and an unnecessary cost that did not end up helping the sale of the house but hindering it.

And not everyone is as detail oriented as they need to be to complete these tasks without basically causing unnecessary frustrations.

@Mario Cuartas some suggestions would be to add tile or low cost durable flooring, if you have hanging lights, replace with dome lights, replace unnecessary ceiling fans with dome lights, do not provide unnecessary appliances (let tenants bring them), supply a full year of air filters if you have central HVAC, if you have window units even better, have a standard paint color you use for all the rentals so touch up is easy, etc.

How long do I have from being pre-approved to finding/closing on a property without wasting unnecessary funds? 

I used to think realtors were unnecessary with the internet and how well informed I am.

6 weeks seems unnecessary.

The bigger take away to me is for everyone to make a much more through analysis of property economics upfront so transacting in and out of properties is totally unnecessary. 

Negotiation was unnecessary and is often over-rated.

The green dye seems a little unnecessary but I guess it sells.