Honestly xcel has everything you need if you use it properly.The hardest part will be setting up all the references and equations for your specifications.If that might seem a little too much of a challenge for you I would put an ad into your local college newspaper offering $1000 for an xcel spreadsheet that you can build upon and let a college intern/professor/student build you one for weekend beer money.

Every situation is unique and there is not a one size fits all approach to protecting your mother's financial security, but there are some options that each has an upside and a downside to.

I'm not sure how to approach this.

The more adversarial your approach the higher the risk in increasing the cost.To determine the boundaries, check the legal descriptions of the properties in both of the deeds.

I tried that approach when I contacted sellers.

Knowing you have multiple streams of income makes work challenges just a little easier to manage.So glad you've already plugged into the podcasts - just a wealth of information there that helped me so much when I started out - and honestly, it still does today. 

Although South Carolina law provides that claims by the previous owner (the nonpaying taxpayer) are extinguished by statute two years after the tax deed is issued, State Courts welcome challenges to Tax Deeds by others during the first ten years.

How should I approach these leads, please?

How should i best approach the termination letter?

I'm not sure how you would approach your friend to buy their property, but in terms of financing, you could always try for a conventional loan program (lesser property requirements, so you could swing a fixer upper pending how extensive the repairs needed are).