As an engineer,general contractor, construction manager of commercial development here are my tips for your renovation and dealing with contractors.
1. define a scope of work
2. get 3 bids
3. buy the materials have the contractor supply labor
4. set weekly goals and a deadline
5. have a backup contractor ready to go
first off I think you should decide if this is an investment property or your own residence. You will always spend more if it's your residence. No one thing or item will cost that much more but when you add them all up you will blow your budget. instead of tile you will want travertine or marble. you would like true hard wood floors instead of an engineered hard wood, that 1200 fridge is nice but that 2200 fridge is the one you really love.
1. define a scope of work-- the biggest problem is people just give generic info to contractors and say make it nice. think if you asked me to buy you a car and i came back with a used 95 honda civic 2 door. you then would proceed to tell me the things you wanted in a car like the model or make, a 4 seater, leather seats power sunroof , navigation etc. you are now defining what you want.
Go rooom by room and make a detailed list of every single thing that you would like to change. take measurements of sq ft of floor walls etc. do you need to remove wallpaper or does it need to be painted? do you need to replace the drywall altogether? do you need electrical outlet covers ?
Once you have this list you can breakdown things into categories if you want to save yourself money. All electrical work in one column. Plumbing in another column. painting in a column etc.
Next make a list of materials needed for each room and each task. Write all of your scope of work and items and attach it to a copy of your floor plan.
Now you have defined a scope of work and contractors will see you are organized and given them clear direction of what you want. They now can give you an accurate and fair bid.
2. get 3 bids--- Once you have a clear scope of work you can get three bids and compare apples to apples. With a clear scope of work the bids should all be within 10% of each other if one is really high or really low this should raise a red flag. The bids should not be used to call one contractor and say you need to beat this price. You can try and negotiate certain items or see if the contractor will negotiate with you. let the other contractors know why you didn't hire them. This is respectful and profesional. Ask the losing contractor you would like to work with them in the future. This will hopefully earn trust and build a relationship and a team you can count on in the future.
3. Buy the materials have the contractor provide the labor.
when a licensed contractor supplies the materials he has to mark them up to cover the overhead cost taxes , workers comp , insurance, profit. this is typically a 20% markup or more. By defining your clear scope of work earlier ,not only are you organized but now have a material list of what you need to purchase. Tell your contractor you will supply materials and what quantity of materials. this will save you money and him risk of putting more money on the street. By the contractor reviewing your material list and quantities he may be able to advise you if you are buying to little or too much and if say you are dealing with a tile contractor who will supply the grout? this will help you further define your project and will lead to better results.
There are times when a contractor can get materials cheaper than you can. when you ask for a bid ask the contractor to quote it two ways . one just supplying labor, and two with him supplying the materials.
4. Set time frame and payment schedule. -- This really is a part of defining the scope of work. This is a major part and shows you are a professional in understading the value of time and money. time is money in your rehab and consider this when evaluating contractors.
Payment terms define this up front. I would suggest milestones be met before paying a contractor. Never pay money up front unless the GC is suppling materials and this should never be more than 10% of the contract. If the job is small say for a painter then pay him once the job is complete and inspected by you.
5. have a backup--- somewhere and sometime for whatever reason some contractor will not be able to perform as you agreed to. This is where dealing wth the contractors you didn't hire in a professional manner can come in handy. They can take over a project and hopefully prove themselves that they can do a good job for you and hopefully become your go to team player when you rehab other projects.
You are spending time doing some of the front end work and not waisting a contractors time who will try and read your mind and figure out what you want.
All of these tips Should help you define your true scope of work, allow you to get more accurate bids, set more realistic budgets, better analyze deals, be more organized, and make more profits.
Hopefully this helps