The white powdery materials are mineral salts (likely calcium carbonate) formed by efflorescence, salts brought to the surface of the block by water leakage and then combined with CO2 in the air. The exterior of the foundation should be exposed and waterproofed. Not cheap.

For those wanting to know more, listen and read Dr. Lstiburek here.

There is water coming into the basement, and that should all be repaired. It could be very expensive, or it could not be so expensive, depending upon the cause of it.

It's efflorescence. Very common with unsealed concrete block walls. It is caused by water seeping in from the outside. It can be painted with a sealer product on the inside. Looks nicer, but it will not solve the problem. It will only mask it for a while.

If the building is around twenty years old or less, it should have a drain tile system around the base that will allow ground water to be drained away. Often, this system is blocked by sediment or the pipes have been crushed by careless construction practices. It needs to be dug out and repaired or cleaned. If the structure is older than this, one needs to be installed. This is dirty, nasty backbreaking work.

If you continue to consider this home, you will want a foundation specialist to conduct an examination and give you a quotation for remediation. You can use this quote to reduce the cost of your offer. You can require correction as a condition of closing.

It's not the end of the world, but it needs to be corrected.