Taxable Bonds For My Sisters Account?

I have $143,000 that I am taking care of for my sister and Morgan Keegan told me to buy taxable bonds then that way I can give my sister an income every month. He has bought $25,875 worth of taxable bonds so far and I noticed on the statement they only pay every 6 months. They are for 2040. I am 70 years old and my sister is 66. Isn't that a little long and I was told I could draw an income for my sister every month on bonds and was wondering how can this be if they only pay every 6 months? Also looks like I am the one who is getting stuck paying for the tax's on taxable bonds out of my pocket. I was planning to give my sister $350 to help with her Social Security money. She was also thinking about buying a small house with this money. Should I let him put the rest of the money in bonds?