What is you normal price?
My calculator doesn’t have a “normal price” key.
I’ll take a WAG assumption and say, no.
If that works out to an acceptable amount, you don’t charge enough for a normal home inspection.
We do not inspect sq.ft, we inspect buildings and what is in them. If you charge plus $50 for a four-plex, why are you using plus $100 when you have 1/5th less work to do when they are all together? Or do you have 18 roofs to access, 18 attics to crawl into etc.?
Based on your formula, you should be charging plus $5, which won’t likely work out either…
How are you going to write your report? Eighteen separate reports, or lump them in together. That makes a bigger difference than anything you do on site and should be considered. .
It isn’t likely you can get 18 units done in one day. How will that affect your overhead? Like Larry said, simple access is not simple.
I wrote a spreadsheet for commercial inspections with hundreds of variables to plug in. Seeing you don’t do many of these having one of these is not practical. I would look at the building with respect to time ($/hr) rather than sq.ft. If it seems acceptable to you, go with whatever you feel is good for you. If you undercut yourself, chock it up to educational expense. You’ll do better next time you get one of these.
Your asking for an answer no one can give from here. We can’t see what your going to have to deal with. If you just use one variable (sq.ft), like many inspectors do, your not going to get very far in this business. You will over bid and never get the job, or under bid and not pay your expenses. Remember, your up against others that try to do it the same way. If they under bid themselves, you won’t get the job. If you undercut them you won’t be able to pay your taxes.
You can make a lot of $$ in commercial work if you can get the job. But you won’t get the job when others are bidding blindly by going on the web and asking people who know nothing about the project, how much they should charge… You don’t need every job, just because it’s a potential big one. So charge what makes “you” money.