Trading Up or Downsizing - Strategies

I was having a conversation with a buyer today who owned a condo and wanted to trade up to a larger house. The difficulty was she needed to sell her condo first to buy the new home. Then of course she would have a very short window to buy a new home. This probably reduces her chances of finding a good deal or the perfect home. What's the solution? She can refinance out the downpayment of her condo, buy the new home and then sell the condo. She can also rent the condo after buying the house. Finally, she can buy the house as a rental for a while and then move into the house in a few years when her income will better support it. There are always good solutions if you do some brainstorming.