I tried not to get involved; I won't get into the architect/LA/Engineer, etc discussion. I've been in the design and construction industry for 35 years as a licensed professional and have my opinions but the gamut of them has been covered above. But, I do think I have a constructive suggestion for you.
For your budget of $5-$7K, I'd not spend much, if any of that on an LA. Outside of the competence aspect, I think cost of the services will be a major detriment. A decent design by an LA would run 1/4 to 1/2 your budget. 25 years ago, I charged $1200 to $1800 for a residential landscape design by the LA in my firm. Costs haven't gone down since then for quality work. And, they might tell you you can't buy the materials in their plan for what remains of your budget. Professional services are worth it if you need and can afford a professional job. In this case, I think the impact on your budget would outweigh the benefit.
I'd carefully draw up a site plan, to dimension of your lot with house, walks, and other features located. I'd do it at a 1/8" = 1 foot scale or even 1/4" = 1 foot. Take a number of pictures. Print them out on decent size and make sure you get good perspective, and include views of and from adjacent properties/street. Pick a nursery or two that you want to deal with and go discuss with them. Tell them your goal of $5 to $7k. That's enough to get their interest. Ask them what a good time to meet with them is; don't go in at the busiest time. Get some advice from them, walk the nursery yard and look at and discuss the plants. Take their ideas, do some research of your own on line, look at yards around you and in neighborhoods you like. Decide on what features you want, and make sure you have enough room to make them work.
I think that you can readily come up with a quality design within your budget with this approach.
Postscript: The picture you posted loaded on my computer and now I see you already have a scaled plot plan. That's a good start; the pictures would be the next step.