I am not deducing the additional interest I've had to pay for privately borrowed money, extra project management fees, taxes, insurance, etc that I've had to pay due to the delay. 

Many borrowers don't expect that one.Cheers!

I've heard of hard money from lender to the institution needing the funds but not straight to the borrower.

We did our first flip on credit cards and money borrowed from friends.

I haven't used one yet, but these allow you to borrow construction costs.

Main similarity is that all 3 allow the borrower to include rehab money in to the loan.I would recommend using contractors that have earned the accreditation as a Certified 203k Contractor.

When you spread fixed costs over a larger loan amount, it becomes more cost effective and the Lender is sharing risk with the borrower (vs. an all cash deal).  

The Solo 401(k) also has the advantage of being more favorable for real estate investments using debt-financing such as a mortgage - as the 401(k) is exempted from a small tax called UDFI that an IRA would pay on the percentage of income derived from the borrowed money.So, as you continue your research and get feedback here on BP, think about what type of program will best suit your needs and be sure to ask questions along that line.

Would I be able to talk to a lender to get an idea of what I can borrow without having a particular property in mind?

We qualify borrowers by DSCR (Debt Service Credit Ratios).