Select a taxonomy parent ID based on the current node type for shared field declarations in cck
Apparently, I am answering my own question. This may not be the best solution (the drupal way) but it works and at least for the meantime I can continue the project. Here is how I solved it:

arg(0), arg(1).. will always refer to the current url arguments. so arg(0) will be the first arg after the siteroot, arg(1) is next.. etc..

With my problem, when you are editing a content type here is my current url path for example: http://localhost/mysite/node/add/commercial-for-rent, where arg(0) = node, arg(1)=add etc..

simply posting this to php snippet worked:

if(arg(2)=='commercial-for-rent' || arg(2)=='commercial-for-sale') return 798;
else return 799;

That's at least as far as the url pattern goes. ../node/98/edit is when editing the content which is again this solution will no longer work...

As I said this is not the best solution if there is anyone out there who has better ideas please do tell me so I can edit the snippet and solve this the drupal way.