You catch more bears with honey than you do with vinegar.

Just degreese with vinegar, windex.

If you want to put more time into it, I would replace the valve or soak it in vinegar for a day to remove deposits.

Instead of Drain-O which can cause problems farther down the drain line, the old remedy of baking soda and vinegar still works well.

"you get more bees with honey than you do with vinegar"

You need: gallon of vinegar food grade, micro fiber rags, big box baking soda, cruddy throw away rags, mop, soft brush, gloves, old used toothbrushes, 2 buckets, soft scraper, hot water, pledge multi surface cleaner.

@Shyam PanchalIt all comes to Cash flow .If you are buying this ppty as a rental i would look into is this a killer deal to pass.From the conversation it seems you are buying a top of line ppty which has some minor and some major issues .Any one can say donot pass it on ,it is hard to find pptys as it is a sellers market,that doesnot mean you have to buy a rehabbed ppty (possibly a lipstick on a pig) and then throw money @it again if it is a skinny deal.A NO DEAL IS BETTER THAN A BAD DEAL.Water heater i would not worry too much will cost 400$+LaborThe AFCI needs attention bcoz in most cities in texas a remodel will not pass city rules if a new breaker box is not installed ,try negotiating with seller on it.Either he puts afci or you get a reduction .It will cost 1000$ + laborMold is a concern.How was it fixed ask if they got professional remediation.Ask to see proof.If proper mold treatment was not done and you do like someone said just brush it off with vinegar or stuff you are on the hook if your tenants get mold in their system.Now it is on you to professionally remediate mold for your tenants (expect couple of 1000$) else you are looking @ a lawsuit down the road if the tenant know what they are doing and trust me tenants will If you have inspection contingency on your contract i would fig out how much the repairs cost and negotiate based on that.

And No- bleach, vinegar, kilz, foggers, will properly remove mold from a building, it needs to be removed.

Finally steam cleaning with vinegar and water took the odor out better than the cleaning solutions.

If the grout is stained, you can try vinegar and baking soda as well (it will foam once mixed together),  I've also used Mr Clean magic eraser.