It's OK to re-use the drain pipe for that valve, if the existing one is in good shape.If the existing heater has flexible water hoses on the input and output, replace them as well. 

The decision making is local and the duration is flexible.

Other reasons include need for flexibility, believe that they end up spending less long term due to maintenance, they don't want to deal with maintenance, moving into a better school district that they can't get afford a down payment in, and the list goes on.  

I’d think there are lots of $150-250K options right around you which would give you more flexibility to view it, manage it (if you want), and handle bigger issues if they come up.

I have a very flexible Nursing position so I can work the ground area pretty much at my leisure.

4) asking about other jobs and being flexible on schedule breaks to accommodate5) being onsite a lot (this could go either way!) 

Be careful about this strategy if it will leave you unable to meet those criteria or without the financial flexibility to keep going if/when things go sideways. 

Real Estate is flexible enough that you can find what makes you happy in it and then become successful in it.

I am fairly flexible in regards to the down payment as long as the investment makes sense (with good ROI), so anywhere from 30k - 100k would be acceptable range for me. 

That can be a good place to be and allow you a more flexible schedule to spend as much time with your kids while they grow up and help facilitate their extra activities.