Answering the first question, we can say that when addressing the designer, you will receive new ideas, a whole set of drawings and find out what will be the result. But on the other hand: firstly, the designer must pay, secondly, not all designers are truly designers, and thirdly, the drawings do not always correspond to reality. So if you have enough money, then you can use the services of a designer. But there are many ways to change your home without its services. The main thing is that you have a plan (drawing, drawing) in which your future room will be depicted.
Turning to the second question, it should be noted that at the moment there is a huge variety of offers on the market: from large construction companies to ordinary teams of self-taught builders. A good construction company always offers excellent services, but, as always, they are worth the money. With the rest of the organizations at times is not necessary. If you are lucky, the price will match the quality. So, choosing those who will change your home, carefully review the portfolio and prices, read the recommendations and reviews, and also just look at the builders (not always appearance is deceptive).
And here we are closer to the most interesting question: how to avoid unforeseen expenses?
Starting repair, it is necessary to decide on the future budget. It is necessary to take into account the cost of the designer, the purchase of building materials, as well as payment of the builders. But no matter how you all calculated on your own, any unforeseen expenses constantly appear. And they make up about 20−30% of the cost. And in order to reduce unnecessary costs, you must first make an estimate (preliminary calculation of the cost of repairing the room), which will calculate the amount of work and the amount of building material needed. The more detailed the estimate is, the better. The cost of working tools should not be included in the estimate, since any self-respecting team works with its tool. Estimates should be carefully studied and signed by both the customer and the performer.
It is one thing to compile and verify an estimate, and another thing to make it true. Currently, there are many ways to fool customers. Here are some of them:
Overstating the cost of construction work. The cost indicated in the estimate is higher than the average market value.
Indication of incorrect amounts of work. The volumes indicated in the estimate are higher than the actual.
Failure of the work specified in the estimate.
Poor quality work.
The use of excess materials not listed in the estimate.
Overstating the cost of building materials.
Use of cheaper materials.
And so on…
Conclusion: it is necessary to make a plan (drawing) of the future premises, to make an estimate of the repair. With this documentation you have the opportunity to hold an open tender. Choosing a construction organization, carefully read the contract and, if necessary, make additions. The contract should reflect not only the construction work, but also the deadlines and responsibility of the contractor. In the process of repair work, monitor its production and reasonably accept the results of work.