As for the actual yield on loans, there is no lower limit beyond the fact that there are fees to lend and return your coins to and from these lending contracts. Those fees are currently quite high, so it is in your best interest to plot those out when calcuating returns.
https://www.voice.com/post/@osaemezu/aave-lend-a-beginners-g...
https://blog.coinbase.com/a-beginners-guide-to-decentralized...
As for the actual yield on loans, there is no lower limit beyond the fact that there are fees to lend and return your coins to and from these lending contracts. Those fees are currently quite high, so it is in your best interest to plot those out when calcuating returns.
https://bitinfocharts.com/comparison/ethereum-transactionfee...
https://ethgasstation.info/