It is one thing to prefer cash but quite another to only accept cash.
1. The building can not get financing
2. The seller priced the property too high and knows it won't appraise and knows a lender will not loan at the sale price.
As an all cash buyer, you will lose your deposit unless you have a financing contingency. It is in the seller's best interest. There are advantages to a buyer that can pay all cash but not when it is required unless it is being sold below market value.
In answer to both your questions, some sellers prefer a cash deal because it's a quick closing.
In regards to pre-war buildings, it's a matter of preference. In some cases the rooms are larger, but it comes down to individual preference.
RE: Mice/Roaches ...that can happen anywhere! It has nothing to do with the age of a building.
Halstead Property, LLC
770 Lexington Avenue
New York, NY 10065
The caveat is don't go in alone. Get professional help from your local Realtor. They will advise and guide you on many aspects of purchasing prior to any offer. Good luck.
If you would like me to check a specific building as far as financing goes, please feel free to contact me.