If the farm has been in operation, start with existing tax returns. They may be your best source for an estimate of the income that is possible.
I'm trying to get 150 acres going and I can absolutely say hay will never pay for the farm, let alone produce replacement income for our current jobs. You have a different situation, given the land is free and equipment is there. I am paying for both so let's take it out of the estimates.
My input costs for hay ground, about 40 acres, runs about $10 per 4x5 bale. That doesn't include machinery costs or repairs. I sell only hay stored dry, so I get at least $20 per roll during the season, but I usually get $30 if I hold till winter. Let's say you can hold all the hay till winter and fetch the best price. There are a lot of factors here but lets say you can produce 400 good bales a year, so you net $8000 after hundreds of hours of work. That might cover your taxes and insurance, but not your food and utilities. You said it has alfalfa, so it is most likely a small square operation, with higher prices than grass hay, but it also has higher maintenance costs and labor input. Bottom line, I doubt it will replace your current income but all the effort may, may let you keep the farm at no added cost to your existing income - except for the hundreds of hours of sweat and stress that you put in.
Without specialty niche products and clever marketing, I doubt you will make 80 acres produce consistent income to replace off farm incomes. That being said, let me say this- what is a farmer?
The way I see it is a farmer is really not a job title, it is a term to fit a conglomeration of work functions. A farmer is a biologist, mechanic, welder, machinist, lawyer, engineer, environmentalist, salesman, market trader, manager, horticulturalist, husbandry, accountant, weatherman, and probably a hundred more things.
For all that, if the stars align perfectly, a farmers profit is usually measured in cents per unit produced. In my own case, negative at the moment until land is paid, fencing is bought and installed, and equipment is sufficient to move to maintain or replace mode. I am pretty good at the math side but I will not calculate it in dollars per hour worked for fear I might have a breakdown. I honestly don't know how a full time farmer does it. Someone once said the fastest way to lose a million dollars is to buy a farm. Oh, one other thing you will need is at least a years worth of operating capital to start.
Basically, you will have to want to do it because you and your husband love it. If either of you have any ideas it will just be hard, you are wrong. It will be excruciatingly painful. The only way you will make it is because you love it, can't go to bed without falling asleep thinking about it, and dream it while doing anything else.
I'm sure there are others here that will provide more guidance, but be sure both of you are in love with farming and not the idea of farming.
I'm in no way trying to discourage you. I hope you find a way to keep and run the farm. I may be losing my shirt at the moment trying it myself, but maybe I'll be able to leave my kids something more valuable than a bank account or a house squeezed between two other houses. Besides, if you can't tell, I LOVE farming!
