That's an impossible question. How much of the framing is known/visible? How much can be opened up ahead of time? How good is the engineer doing it? How fast is the drafter? It's a very firm specific question. If you're just starting out on your own, how long has this sort of project taken you in the past? Start there. If you come up short, either plead with the owner to pay you more or take it as a learning experience and increase your estimate for the next one or learn to work faster (or, better yet, both!).

Framing is unknown. Area is 19’x15’. Framing is 2x6 16” OC. Basically I’m going to do a ledger board on each side and connect it to framing studs with lag bolts. 2x12 SYP floor joists. 2x4 frame walls to build out bedrooms.

3-4 sheets (general notes, plan, elevations, details). Does that help?

If you're trying to get an estimate for what a structural engineer would charge for stamped structural plans, you're best off asking a local structural engineer.

Just for fun, though, based on the very limited information that you've given, I would ballpark this at about $3,000. I'm not sure why you care about the number of hours, but for me this would be about 20.

Adding additional load from the new floor to the exterior walls is probably not a big deal, although I would want fire blocking added between the existing studs at the new floor location. I would also check that the existing door headers can support the additional floor load. Where new floor joists would be supported by what I'll assume is an existing beam located below the railing, that beam will now likely be overloaded and will either need to be strengthened or replaced. From there, everything supporting that beam down to the foundation will need to be checked and perhaps also strengthened/replaced.

Assuming that the new bedrooms will have windows, modifications to the exterior wall will need to be made. In particular, new window headers and support studs will be needed. The concentrated loads from the supports will need to be checked on the door headers below, etc.

That's roughly how I'd approach this. Beware of anyone willing to do this for $500. If you find somebody like that and the long-term quality of the project is a concern (hopefully), be sure to mention a few of the things noted here. In particular, it's important that they check the load path all the way down to the dirt.

OP, I assumed you were a builder for this project looking to hire an engineer. In any case, the description above is roughly how I'd approach this. One minor thing, I'd use wood screws and not lag bolts for the ledger connection.

engineerED930, how long does it normally take you to finish a job like this?

What Eng16080 said. I charge roughly the same including 1 site visit (assuming not too far). You have to figure out the existing structure. The loads going to the exterior walls are easy. The loads going to the middle is tricky to figure out especially if you have a finished basement. Part of my fee is also going to the site visit and give them my professional opinion. Sometimes what they want isn't realistic and will cost too much money. Sometimes they have to live with a column in the middle or a dropped beam instead of flush.

This is usually a $1500 dollar job for me on (1) 8 1/2x11 sheet. Might take a 1/2 hour site visit and 2 hour max of design and drafting. Really depends if you can get a favorable joist direction that does not require a bunch of new beams. Also, if it has a basement, it can complicate things.

Can I interest anyone in a race to the bottom?... Oh wait, never mind, it looks like it has already started without me. LOL

engineerED930, since we're all sharing here, what will you charge the homeowner to build this? I am assuming you are the contractor bidding on this.