A few more details would help . . .
I'm a beginning sailor, just bought a Lido 14'. I'm going to sail it on our lake and I want some recommendations for using a trolling motor?
What size lake? Just a thought here but if you add up the cost of a trolling motor, a good deep cycle battery (or two) and a charger, you've spent almost enough to purchase a 2.5 to 3.5 Tohatsu/Nissan ouitboard. The outboard would provide a lot more power and range. Another thought is if the lake is not HUGE, install some oarlocks and get a couple of oars.
Otherwise, without additional info, you'd probably need 50+ lb thrust and a good 90-100 AH deep cycle battery.