bgav, you used the term "sinkhole" but the general discussion does not indicate that a sinkhole is likely. It's probably a hole caused by surface erosion in which case solving erosion problems would take care of it. While slopes can present erosion problems, these are not unsolvable. Usually, all that's needed are groundcover-like plants whose roots form a network that holds soil in place and whose tops protect the soil surface from slamming rain and flowing water. Sometimes it can be difficult to establish such plants (if rain washes them out before they are established,) but it's not impossible if one dedicates one's self to the process. I would consider retaining walls necessary only if the grade is so steep that it cannot possibly stay in place as a slope. Do you have slopes so steep that no planting can possibly hold them? Look around the neighborhood and see if like slopes exist and if they are stabilized by plants. It such slopes exist elsewhere, they can exist on your property as well. You would only need to find plants capable of stabilizing them and working with your overall landscape goals. While the last picture you added is still too close-up, the slopes seen in it do not seem overly difficult. It's likely that if you have plenty of places where retaining walls COULD go, but limiting them to places where they are actually NEEDED might be a better strategy. We would not be able to suggest where such places might be without seeing some overall, wide shots of the areas. If you seek advice about where retaining walls could go from contractors who sell them, it is likely you will be advised to add a lot more walls than you need. Consider hiring a landscape architect or a qualified designer to advise on where walls would make the most sense.

Red flags everywhere. TANSTAAFL. You don’t get million dollar work for $1.98 pay. Any Pro will run for the hills reading that. Which is what sounds like has happened. Take a hard look at your expectations and approach. Or you’re going to be paying 2M for million dollar work just because of the pita tax that appears to need to be charged here.

I think a single french door with glass panes and frosted to give Mom privacy would look nice.

We have done two of these and are getting ready to do the third. Here's my two cents: - Bathroom: You'll need to be out of the bathroom while they do the plumbing and tilework, at a minimum. Find a contractor who can keep to a tight schedule, and this can be 1-2 weeks. Use the people we used, and you're looking at months... You can absolutely work with a vintage tub (and should, if it's in good condition!) but it may depend on the scale of what they need to do for the plumbing repairs, and how accessible the plumbing is from below. If the valve itself needs to be replaced, they'll need to take the tile out for that (though we did that as a single-day project in ours and it worked out). Also, you will need good access to a working bathroom if you want to live in the house during a kitchen remodel. - Floors: This is the one we're ramping up to do. The flooring people we've talked to all want the furniture out of the entire space to do the floors all at once. We are doing the public rooms but not the bedrooms (where the wood is generally in better condition) to minimize how much needs to be packed up, but will still need to have movers and possibly a pod involved, which is a pain. YMMV depending on what kind of shape your floors are in. I would definitely prefer to wait until any remodeling is done to redo the floors (too much potential for damage). - Kitchen: Easy to live in the house during this one, if a bit of a pain. But given that you're doing other work that requires being out of the house, it might be most efficient/cost-effective to just be out of the house entirely and do it all at once. Friends recently did the same set of work that you're looking at and were able to be out for three months and get everything done at once. Their GC waited to start until absolutely everything was on site and all permits were in place, and that seemed to work well. I do think it's possible to be out for just the flooring depending on the scope of the bathroom remodel, but you'll need to start by talking to a contractor to better understand exactly how much work you need to do, and if this needs to be a gut (in which case you'll need to find a rental).