I am near retirement from the 9-5 and would like to diversify into rental properties.

I asked if they would consider seller financing on the property and they said, “yes”.

I have a tenant who I believe to be on some type of heavy drug like herion, or meth ...I recently inspected the property it was full of garbage everywhere some hording, it's just trashed. 

However, only the time you personally spend on managing or coordinating the property counts.

Is anyone having issues with Zillow Rental Manager, where you get to the last step before publishing and it will not allow you to continue?

Every time my wife and I purchased a property the numbers never looked attractive on day 1. 

(Keyword research, competitor research, surveys, speaking to prospects on how they heard)If your research proves that there is demand, I would recommend you  to either hire a good agency who has proven track record in your industry or  hiring a fulltime  employee with relevant seo skills who can manage this.SEO/Paid ads with consultants or agency would be challenging as the results depends on various things such as your website, market, content, offer etc.

I suspect they won't be able to make it and being a new landlord, don't have any experience with this aspect of property management.

Is there anyone having success with any specific marketing strategies in Fayetteville, NC and having success? What methods are working best for you? 

You can use conventional financing, up to a fourplex, and if you live in one unit you may reduce some of the property tax for the space you live in as it is your primary residence and you can also buy with very little down as opposed to buying it strictly as an investment property.Duplexes are a great option and you generally also always have at least one paying tenant and can be bought similarly.