I feel this is a healthy addiction though as long as you keep the rest of your life balanced!

We had a sprinkler system at a house that we though had been removed, but it turned out all the heads, etc were just buried under gras and soil due to disuse.

I'd put my money on the fact that they put the addition on spread footings without doing much to improve the soils under them. 

Large, transverse cracks are the larger worry, as they are more likely caused by differential settlement in your foundation (the soil underneath a portion of your foundation wall dropping, while the rest stays more or less where you want it - look for a "stair-step" pattern in your mortar joints), water trapping against (or worse, inside) the wall and expanding during the winter freeze cycles, or insufficient steel reinforcement - which is not uncommon with concrete masonry, particularly if the house is pre-1950s (ish). 

,Soil characteristics, vegetative cover, and status of mineral rights, andOther factors affecting value.For each comparable sale, the appraisal must include the names of the buyer and seller, the deed book and page number, the date of sale and selling price, a property description, the amount and terms of mortgages, property surveys, the assessed value, the tax rate, and the assessor's appraised FMV.The comparable selling prices must be adjusted to account for differences between the sale property and the donated property.

The terms i wrote above are ours we believe their decent and it allows them to get to know our work with great guarantees. even if we have cash capital we always believe in a healthy  leverage and would use a hard money loan.

I imagine it’s a different story if you’re buying turnkey and don’t have a healthy rehab budget...Good luck!

If the sister is young, healthy, and has stated she's not leaving the discount would be significant. 

Ensure that you put the adequate sub base in place and rent a tapper/soil compacter, form the pavement area, order the concrete from your local concrete plant and place it yourself.

Those all look like healthy growth markets.