Welcome @Account Closed! Love your style of writing btw. So, here we go...
If you are buying a foreclosure, some may be in better condition and are able to bank finance while others are in serious disrepair warranting alternative financing (hard money lenders, private lenders or cash). In my market, only cash offers or what appears as a cash offer will get accepted on foreclosures due to the speed to close and confidence in closing. You can try the hard money lender list BP offers or search on google for your area. HMLs can do a % down of the ARV and finance your rehab too depending.
Refinancing usually has a 6 or 12 month seasoning period depending on your local credit union/bank and usually they require 1 year lease.
Lenders- if you are going conventional, and have properties in your target market that would finance (ie no roofs that need to be repaired or major mold issues) then just start talking to local lenders and see what their requirements are. Do they keep loans in house?= can make smaller loans or bundle a package of SFRs. Ask other investors in your area who they use for lending.
The key to the BRRRR strategy is buying at a low enough price, factoring in realistic rehab budget, refinancing at 75% ARV to give you a spread to cash out and roll into the next purchase. This can take time to find the right priced property in certain markets. Say you purchased a property at 40k put 50k in=95k all in. Putting 15% down with a HML=13,500. If ARV is 150k, then refi with long term local bank 75% pulling out 22,500 to roll into the next property.
The more deal you do with HML the better the terms can be, so start with one and build up your experience.