Unless you live in a state where deposits have to be kept in a separate account (google) I would open 1 business account and a credit card for the rental property. 

-Would it be better to ask for the down payment loan and construction loan from the same party, or are there any advantages to seeking loans for renovation costs elsewhere, such as HMLs or even credit cards?

They are a Purchase & Sale Agreement, Title Report, Power of Attorney, Disclosures, Closing Statement, Payoffs and a business card to a good attorney to get you out of the mess you will create if you try doing this on your own.But use somebody, like us, that actually knows what they are doing to learn this.

Just watched a CI webinar about the new PINV4, had my credit card in my hand seemed, but decided to research before pulling the trigger.  

If you are to go this route, here are some of the best 0% APR business credit cards.

Also, sometimes you hire uninsured people, e.g. a cleaning crew at the end, so having the insurance is rather justified at that point.For better or worse, if you can pay everybody with a credit card, you don't need to file 1099's..

As soon as I create the LLC, I go to the bank and open a checking account, savings account and apply for a credit card in the name of the LLC.

No seasoning.Key Bank, FLorida flexible lender, HELOCs on second homes and rental properties. 90% LTV on primary.PenFed - max 3 other properties, 89% LTVRegions- yes HELOC but no LOCSCCU Florida 70% LTV, 6.25% interest only, not LLCSound CU "non-owner occupied HELOC, capped at $150K and interest rates are prime + 2%, 3% or 4%, based on credit, not to exceed 70% ltv.”TD BankTIAA Direct was EverBankTower FCU, all states except TX, max 45 DTI, green card ok.

My credit score is 550.. no bankruptcy, no foreclosure, just a bunch of credit cards.

Please know that many investors use this approach, so homeowners get mailer and post card fatigue from all the spam mail.