At it's basic level:

Assumption: Asking the bank to turn the loan over to you and going through the normal underwriting process, credit, income, DTI ratio etc

SubTo: Taking over the loan without telling the bank, no underwriting, no credit check, no income verification

Both have risks, but it's not my intent to be detailed in this post. Simply put, there is a very big difference. Subject To is a wonderful tool, for the right circumstances.

So, if someone is teaching you to buy properties using Sub To, just be aware that they aren't explaining the risks to you and that is where the danger is. We spend a great deal of time dealing with our students explaining those risks and how to avoid them and a simple one is to be properly funded. You can't borrow your way to wealth. It's incremental steps.