It could be many reasons, sometimes it is out of your control like roots, collapsed or broken pipes. But many times it is because of things we throw in the pipes like baby wipes, objects, towels, grease, large amounts of paper, etc.

Toilets are easy to replace the parts inside the tank like the flush valve, fill valve, and tank to-bowl gasket. But, you have to evaluate the costs of replacing these vs the full replacement of the toilet. Some people replace the toilets to be more updated, or to have high comfort toilets.

It could be problems with ventilation or stoppage problems. Stoppages have many reasons like old cast iron pipes corroded, roots, objects, etc. These situations do not allow the pipe to breathe and you can hear the gurgling through the pipes and running very slow.

Yes. For example, you can update the faucet, the disposal, paint the walls, replace the countertop, the backsplash, etc.

You can paint the cabinets completely, change the pullers, or paint the cabinets and replace the doors.

The owner is who decides what to do in their house. As contractors, we give pieces of advice on what is code friendly or what is against the code. We do not recommend installing a laminate floor on a rented house at all. 90% of the kitchens have tile floors. It is simple, durable, and stronger.
If a pot or a knife falls against a laminate floor, it could damage it. But is you do not go to the kitchen too often or you do not cook, then laminate is an option to consider.

We have installed osmosis systems inside cabinets close to the kitchen sink. Keep in mind that you can find from 3 to 7 stages which means many small filters. You should be careful with the stage you are going to buy and the space available to installed it.

Installing a french drain piping, gutter collectors, and catch basins are one of the ways to go

One of the ways to extend the life of the pipes is by installing a filtration system like water softener, carbon filter, sediment filters, etc.

Yes and No, an emergency is a partial solution to solve a major problem created. For example, a stoppage created by wipe towels or an object in the sewer is an emergency that can be solved with the snake. But it will become also a repair if the reason are roots through the pipe. In this case the tile needs to be cut, the slab needs to be opened, cut the pipe, remove the roots, repair the pipe, cover the hole, apply anti thermites solution, patch the concrete, tile next day the floor, and grout it.