A:Answer QB doesn't handle interest calculations (AFAIK), you need to have that figured out ahead of time. Its a full featured accounting package generally for businesses. If your only activity is a loan you gave to a person who bought an asset from you, I'd think Quicken could handle that. Also that's the sort of thing I have setup in Excel, but it is tricky to make the interest calculations accurate. Typically people using QB have a bank statement with interest and principal payments listed for input, or link to a loan account automatically.
FYI I am accountant/bookkeeper for multiple businesses and have done my own personal loans on excel.