1. You can fill in the lease yourself, but use the standard lease template. If you do not have one, GOOGLE and you can find many examples.
2. No need to sign lead related document if the house is built after 1978.
3. Check their credit score.
4. golden retriever (70-80 lb) is kind of big.If you have lots of carpet or wood flooring in your house, you may see lots of wear and tear after 1-2 years. If you have tile flooring in your house, probably OK. You can charge them extra deposit, like $200 to cover potential damage, and charge an traditional rent, like $25-50 a month in addition to the regular rent.
Good luck.