For example, there were some cracked tiles in the kitchen and they said it could be a slab leak.

Also, you will want to be sure that it is a wise investment.If it doesn't make dollars it doesn't make sense.Some utility companies have rebates and you'd see a HUGE $200 credit from the IRS for installing windows (sarcasm).

I'm curious to know if we can just get new copper lines installed for the unit OR do we have to replace the whole AC unit.

I'm pretty sure you don't need permits for paint, carpet, refinished hardwoods, tile flooring, windows, new int. doors, ceiling fans or light fixtures etc.Married life is agreeing just fine.

The IRS gives you the option in a failed 1031 exchange that goes across tax years to treat the sale as an installment sale with the proceeds received in the next year.The impact for you is that if your accountant files it as such you will not owe the tax until April of 2024

In addition, the area below the sill was all disintegrated   We replaced the  window sill with a fabricated Corian sill (a local place did that)  and we also put a broad  Corian apron below it to replace the tiles and wonder board that had disintegrated.

Whoever installed it was careless and left chunks of concrete and rocks set next to the line which over time rubbed and broke the line. 

I've installed tile backsplashes in an effort to curb the damage and make it easier to clean, but in some cases it's a huge amount of work to clean up.

Be aware that installing low-flow toilets can lead to more clogged toilets.  

Sure painting, laying flooring and installing light fixtures are easy.