If your home is paid off - and it's worth $400k
Then you have it on easy street -- I dont know who you bank with but they may be a good place to start -- find a place that will approve you for a HELOC (Home Equity Line of Credit) and your house is used as collateral --
The interest rate they quote you will be based on credit and then how much of a LOC (line of credit) you request and are approved --- then what drives the rate as well is how much that line is as a percentage of your primary residence Value --
IE you take a 60% LTV so $400k * 60% = $240k HELOC -- the HELOC can then literally be used as a check book - normally fees are very minimal to set these up -- app fee is normally just to cover the cost of the appraisal on your house. You typically do not pay any money or fees unless you are using part of the credit line --- if you use it - you are then charged interest for the amount outstanding -- you can pay interest payments only - principal and interest etc.
So you are in a good position - if your bank does not provide one - call around to some of the more local/regional banks that you know have been around a while and are well established - you can probably find plenty of banks willing to set one of those up.
You could use the HELOC to pay for the purchase of the house and the rehab - then when you're done - find another lender and BRR out of it - -- then use the funds to pay your HELOC off and start again.
To have a $400k house paid off is a very good position to be in if you are willing to use it as collateral for business purposes.
This is just a hunch - but if you find a bank willing to lend up to 95% or 90% LTV for a HELOC - I'd take an educated guess that bank will offer one of the better deals to "A" get a HELOC set up and "B" interest rate - especially if you stay in a more conservative LTV - such as 70-75% or less -- each bank will have it's own underwriting requirements - but around where I live - they are really aggressive and friendly on their HELOC terms if you keep your LTV at a certain ratio or less -- they figure that giving you the HELOC with so much value left in the house is a pretty safe bet for them. Anyways some food for thought.