The unit has been cleaned, but we can still smell the cat, and we feel the effects of the cat dander/urine. 

How will either scenario effect cash on cash return and IRR?  

This is in the Palm Springs area and it is a desirable place to live so even if she left, I know tenants are not hard to come by.All of my deals have been "low hanging fruit" wholesale deals with equity cause this is who I have been direct marketing to but now running ads this is my first lead that is not so clean.Is a seller financing situation the best case with a down payment of the balances owed being worked out?

Anyone know of the most cost-effective way to do this?

The most effective method for lead generation on the web is pay-per-click (PPC) advertising on SEARCH engines (google, bing).

If you're serious about wanting to get started, there hardly any more cost effective way to start your investing education.

In effect, I had a partnership, with my parents.  

Consider sending in a 9 X 12 envelope as they can't miss it.Unless you're mailing many hundreds, this can be very effective as it adds value to your service, beginning with "heads up" this us what your house looks like now.

A single member LLC has no effect at all on taxes, unless you elect special tax treatment.

Too much production and your heirs enjoy the fruits of your labor but you and your wife don't.