The problem you may run into is that your 50-75k project may be too much based on the value of the property once the project is complete.
Example, If you are buying a home, say $200k appraised, $186K purchase price. You put 20% down, $37200, you will have a 1st mortgage of $148,800. Assuming you have good credit, 700 or above, the bank will do it, no problem. Their interest in the property is far less than it's appraised value.
Now you need to finance your project. Based on a $200K appraisal, and your $149K mortgage, you have $51K equity. Depending on your credit score, you MIGHT be able to get a 100% home equity loan, but likely less. What the bank is going to look at is the value of the property against their interest in it. They will not, if their smart, loan $250k against a $200K property.
What you need to look at also is what your final interst in the property will be. Just because you build a $75000 garage does not mean that you can automatically add $75000 to the appraised value of the property, probably more like $30k, maybe.
Don't get yourself upside down in the property or you will lose your **** if you have to sell 5 years from now. Based on the above, you're gonna have $225,000 into a property that might sell for $230,000, which isn't too bad, except that when you sell you'll walk away with $5000 cash, as apposed to the $37000 cash you had into it initially.
Obviously the situation is even less rosy if the house your looking at is only worth $100,000 now.
Also, do you have a house to sell now?? How's the market in your area??
We're in the process of trying to buy and sell, and the market around here ***** right now. We've got a decent house at a decent price, but it's not selling primarily because we can't even get any lookers. Can't sell it if nobody's even looking.................