hello, and debt servicing question

[Kevin Mauch]

Newby here in northern Colorado. I have been shaking several trees l know of and talking serious long term strategies. I have some good contacts that have been in the biz for 45 years. They are old school, cash, free and clear owners at this point with triple digit unit ownership. 

They have been through several 50% occupancy rates cycles in their time. They are telling me that in these down cycles they never would have made it through With a 70% debt ratio without liquidating properties at a very bad time. 

So what are thoughts on a good debt percentage assuming a 20% roi for the long term cycle For rental properties.  I know buy, rehab, rent, refinance works even an average market, but I am trying to plan for a longer term investment than the market cycles. I know the 2+2=4 but I am looking for a formulation of risk leveraged/time factor= not losing it all in a crash. I hope that all makes sense. 

Thanks,

Kevin