In summary - not yet.
If you need to sell your house in order to buy a new house -- and if your house is not already under contract -- then even if you find your DREAM HOME -- resist the temptation -- do not make an offer yet!
If you make an offer on a house with a home sale contingency without your house already being under contract...
- the seller is not likely to negotiate much on price
- the seller may simply reject the offer and tell you to come back when your current house is under contract
- the seller will likely use your offer against you -- notifying other showing agents that an offer exists to try to get an alternative buyer off the fence to make an offer that may not include a home sale contingency
- even if the seller accepts the offer with the home sale contingency, they will almost certainly include a "kickout clause" which will allow them to move along to another buyer if the other buyer does not have a home to sell
So -- if you view your dream home and you are ready to make an offer but have to sell in order to buy -- don't make the offer yet -- instead...
- prepare your house to get it on the market
- list your house for sale
- get your house under contract
- then, make the offer on your dream home, contingent on the settlement of the sale of your house which is already under contract
This may sound/seem difficulty or slow or risky or uncertain -- welcome to the world of trying to sell and buy at the same time! :-) But it can be done and I regularly help folks with this.
All of the advice above is generalized -- if you are in a situation where you want to buy but you have to sell -- let's chat more specifically about your situation and develop a game plan.