Not every renovation / retrofit will need major changes. And for the sake of your client's budget, be realistic with those changes.
Consult on the Job - Talk to the client about what's wrong. What do they want to change? What problems do they see? Set a time for a thorough visual inspection based on their concerns. Charge for the consult, report and inspection.
Qualify the Job - What's the budget for the work? Have they thought about this? If they have no idea, be ready with some ball park estimates based on minor, mid-level and major jobs.
Inspect the Job - Charge out your services for visually inspecting a building and creating a report on the things that need attention.
Advocate for Doing Very Little - If the building only needs some TLC (Tender Loving Caulking), then recommend this. You can refer them to specific materials from your favourite supplier and keep them in your loop. Offer to do the simple jobs for them and quote them for the work in your report.
Create a Standard Checklist for Yourself - For your consult, your visual inspection and your work report, create a simple template that you can use on every job. Keep track of how long the checklist takes to fill out per job and work towards standardizing fees.
Underpromise and Over Deliver - Do a job that paves the way for word-of-mouth references. Be a client service expert on top of your renovation skills.