Every contractor I've worked with has taken 50% up front and 50% when the job is finished. This is normal. One thing I would recommend is you vet your contractor thoroughly--check reviews, make sure they have a legitimate website, testimonials etc...
Protect Yourself when Working with Custom Home Builders Only work with a licensed contractor. Get the contract in writing. Avoid “lump sum” bids. Talk to several contractors. Tie payments to deliverables. Get proof of payment to suppliers.
The NEC4 Engineering and Construction Contract: the most frequently used contract from the NEC family which has been used on both high profile and every day projects such as infrastructure, buildings, highways and process plants.