I know this is impossible to answer with a blanket number, but is there a rule of thumb or conservative figure that most end up seeing?

The lessons that I learned the most, were to be firm with your rules, and definitely follow tenant screening, and don't take crap from contractors.

Are you measuring the incremental rent return on your improvements?

I can learn the rules of footie/soccer by reading the FIFA's Laws of the GameI am unlikely to perform well on game day unless I have a coach who knows strategy.Best of Luck on Your Real Estate Investing!

A special rule applies to students and business apprentices who are eligible for the benefits of Article 21(2) of the United States–India Income Tax Treaty.

I purchased the house for 168K, with a few improvements and upgrades, I invested about 6K more for a total of 174K invested. 

Real Estate prices typically follow 1 -2 years behind oil and gas activity, so hopefully we'll see prices climbing again in a year or two.Our plan is to pick up as many cashflowing properties as we can while the market is down and soft, then re-fi when it improves and recycle the capital into more projects or possibly down into the states on larger deals.

@John CoonOr 50% rule?!

Also, just like anything else the more time you spend qualify deals the better and faster you will become at it, so the practice will improve the process. 

Cash flow is roughly $100/door below market right now leaving room for great improvement.