GREAT advice by @Tiger M.
I laughed out out loud at Tiger's number six (streets named after cities), and at your reply to it. :D
Pretty much every experienced Vegas investor I know wouldn't touch the fourplexes here, due to location within the city. Tiger gave some great reasons why.
Sounds like you have a handle on things though, @Mike Holland , and some good responses to Tiger.
Just to clarify for #1 - your expenses will be 40-45% and that should not be counting your debt service, and, as Tiger pointed out, your vacancy/collection loss will probably run in the 15% range (and that's if it's managed fairly well, otherwise it could be in the 50%+ range), so your total expenses before debt service is likely in the 55-60% range for the fourplexes here.
On #2, don't count too much on spreadsheets that look lovely on paper and then leave you stuck with a hot mess in real life. Talk with some experienced investors as well. Experience is a big benefit that spreadsheets just don't have.
I'm not sold on the idea yet, but it sounds like you're considering the right things before jumping in and getting over your head, so that's a good thing.
Ditto Tiger's advice to come to @Phillip Dwyer 's BiggerPockets meetup, next one is Tuesday evening July 29, would love to see you there and hear more details.