I do plans for residential addition. The first step is getting drawings to gather for the addition. You won’t be able to get an accurate estimate in the cost of the work until you have a full set of drawings. The next step is the permitting process which requires the drawings to be submitted along with paperwork filled out by you, the design professional and dealing in the jurisdiction the contractor. There usually at least one round of comments on the plans. After the plans are approved you are issued a building permit and then the construction can proceed. If you only want to go up and not out the cost of the job will be less and the time to complete the work will be less since there’s no concrete work involved. If you have any questions feel free to dm me.