I read that scuppers are easier to maintain and are a cheaper way to drain flat roofs versus gutters or interior drains.  

Like anyone else, I am sometimes off or flat out wrong.

Hasn't been a big deal for me - just bake it into your #s.Its possible the utility companies might even share approximate #s for past use too, so you know what to estimate in your budget.

Have a property in mind but sometimes listing agents get worried about covering both ends (especially when not getting paid to).In this market, I'd rather get a discount  by bringing my own flat-rate "buyers agent" or use a closing attorney.Offering $750 flat to be my buyers agent for a ready to go deal. 

Does anyone have a good flat fee MLS service they've used?

as was noted above, percentage is not a good indicator of price.There is a kind of a floor - where it's not going to get any lower - for example, "legal" costs could be a flat $400, or $600. 

He used a percentage of 6% instead of a flat amount.

For a short term flips you may negotiate a percentage of the profit, a flat fee, or an interest rate.

Is "10%" an annualized percentage rate or a flat rate of return?

I could definitely see myself carving out a nanny flat for myself, then renting out the rest of the property.