Contact the owner
Firstly, try to set up a meeting with the owner. Talk to him/her about the work they want from you, what material they would like to use and the time frame they want the work to be completed. If they want you to construct a new house, get house plans in order to make a good bid. If that is not the case, calculate the area that needs to be renovated. Go to the local building companies and suppliers to find out how much the materials will cost. You can send the job out for various bids on things such as lumber, finishing materials and hardware.
Think and analyse how much time the project would take considering all factors. Allow yourself an hourly or daily wage to get the job done. Around $20 per hour in labour with the exception of materials is a decent price for a simple construction project. However, you can increase the amount if the work becomes complex or requires extra effort. Discuss this point with the owner beforehand so that he/she does not feel that you are overcharging them.
Gather your numbers for materials
Collect your approved numbers for material and labour approximation for the owner to check. If it is possible, use bidding software so the owner can see the services you will be providing and the actual costs for the materials. This will help build some trust between the two parties. Make the bid to him and offer a warranty that you will maintain the cost for a month as he/she makes a decision whether you are the right person for the job or not. If he/she takes more time, then you will have to update the prices.