Horizontal cracks like the one you describe are definitely a sign of bowing walls. This problem can be caused by a combination of poor foundation drainage and soil composition. Clay soils are known to cause this problem because they expand when wet and shrink when dry. The good news is that there are technologies out there that can improve drainage without having to dig out the foundation and install new french drains. There are also many options to stabilize bowing walls or return them to their original position, ranging from wall anchors, helical anchors, I-Beams, wall braces, carbon-reinforced strips, etc... all of which are less disruptive and more affordable than rebuilding a foundation. Here's an idea. Many reputable foundation repair companies offer free inspections and written estimates, and if they are have been in business for a while, they also have some experience inspecting foundations for real estate transaction purposes. I suggest you call a few of them, have at least one perform a professional inspection and give you a written estimate. With that written estimate you can then decide what you want to do. Walk away, negotiate down or ask the owner to fix. Consider that the house will have to be fixed at some point. I believe the current owner will have to do it if he wants to sell the house. Banks usually frown upon issuing loans to buy properties that have serious structural issues -- even if you are willing to buy it "as is" with a substantial discount. But since you really like the house, it is a good idea to get an expert opinion, know exactly how serious the problem is and how much it will cost to fix it, since it won't cost you nothing to find out. Hope this helps.

The only opinion that counts is the one that you get from the structural engineer that you hire to inspect the home. Ask for additional time for the inspection period, and call the engineer, as well as several contractors post the engineer's inspection to give you a quote on what he tells you need to happen.

I didn't understand a single thing about "right,left horizonal,vertical"and on and on but here's some answeres in general. - What is the best way to fix it? How much will it cost?( You will need somone on site to tell you) - would this crack affect the house foundation in any way in the future?(Not likly,especially if the patio cracked away from house foundation) When and if you demo and repour patio,put an expansion joint between house and patio slabs. - can this crack be fixed by filling and sealing? (Not perminatly) - can this crack be stopped from further movement?(Not likly unless you install piers and/or footings beneath it. Another option is demo slab and repour a new one with proper footings and steel. - is it safe to convert the sunroom to office or it will cause more cracking?(I don't think normal weight of addition will cause any more movment than will ocur anyhow. I wouldn't reccomend adding improvements on the slab. I would leave it as is and put the addition elaewhere or replace the slab before building on it. Bottom line,you will need a pro with eyes on to get best reccomendations. Good luck with it.

Hairline cracks in a newly poured concrete foundation walls are normal and are caused due to concrete shrinkage during curing stages. Hairline cracks 1/16" wide vertical cracks. Some vertical cracks 1/8" or wider could be a sign of distress and they might have to be evaluated.