Being the best house in a Bad Neighborhood usually doesn't make it sell.I don't know the DFW Market - but 55 Days is long for most Texas markets. probably time to cut Bait (Price) eat the loss and move on! 

Usually just the monthly service fee is $5-10 but those costs are relatively minor.

I talked to the local police department precinct involved in the area and the officer thought the right owner could raise the bar for the neighborhood and that the crime they investigate are the usual domestic disturbances or the occasional car break-in and that the neighborhood is pretty good. 

Will the duplex cashflow significantly better than the SFH for the extra work of another set of tenants and maintenance?  

These are usually fairly easy to obtain. 

Generally when you're going to lease option a property, especially with little equity, the property should be in good condition because you may not want to or be able to dump money into renovation of a property and your tenants usually will just want a move-in ready place.

Just remember that you need access to capital to keep doing deals so if you are limited on funds and tie it up in a rental property that makes you an extra few grand a year you may be limiting yourself to doing other projects.

Though, I do have an extra copy that I would be willing to part with if you'd like it.

I have a full time job and I'm considering Real Estate Appraising to both gain skills and earn some extra income to jump start my buy and hold RE investment strategy.

That extra 1.5% down goes a lonnnnnng way towards making this happen.3) Find a Local Expert -- Once you know what you'll qualify for in regards to a loan, it's a good time to team up with a local agent (particularly one who's investor-minded) and they can show you the lay of the land.